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Progress at LAMPFJanuary-December 1991

LA-12437-PRUC-410andUC-910

LA—12437-ER

DE93 005043

MASTERLos AlamosN A T I O N A L L A B O R A T O R Y

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Progress at LAMPFJanuary-December 1991

LA-12437-PRProgress Report

UC-410andUC-910Issued November 1992

EDITORKaren Poelakker

SCIENTIFIC EDITORIAL BOARDRichard L. HutsonMario E. SchillaciOlin B. van DyckD. Hywel White

WORD PROCESSINGJeanne Bowles

COVER DESIGN & ILLUSTRATIONSChristine Weaver

ABSTRACT"Progress at LAMPF" is the annual progress report ofMP Division of the Los Alamos National Laboratory.Included are brief reports on research done atLAMPF by researchers from other institutionsand other Los Alamos Divisions.

Progress at LflMPFForeword

Foreword

The Los Alamos Meson Physics Facility (LAMPF)operated smoothly during 1991. although at ;i reducedschedule due to funding limitations. In addition,accelerator operations ended four weeks earlier thanoriginally planned to allow preparations for the DOETiger Team audit of the Laboratory.

Despite the relatively short running schedule, animpressive array of new and exciting physics results camefrom LAMPF experiments. The high intensity of theOptically Pumped Polarized Ion Source (OPPIS) has madea number of measurements possible. Precision measure-ments of the spin-transfer parameters in np elasticscattering have resulted in major improvements in NNphase-shift analyses. These phase shifts have intrinsicinterest in their own right in describing the free nucleon-nucleon force, and are needed for interpreting the resultsfrom many experiments at LAMPF and CEBAF.Measurements have been made at the Neutron Time-of-Flight Facility (NTOF) of the spin-longitudinal and spin-transverse nuclear response functions. The results show asurprising suppression of both response functions, indisagreement with theoretical expectations. It has recentlybeen suggested that partial restoration of chiral symmetryinside the nucleus may be responsible for the suppression;further measuremen.s of this type, which can only be doneat NTOF. are planned.

Parity nonconservation has been studied in thescattering of epithermal neutrons from compound nuclei.Strong evidence of parity nonconservation in a number ofstates in uranium and thorium has allowed the meansquared parity-violating matrix clement to be extracted.Theoretical work has allowed the weak meson-nucleoncoupling constant to be determined. One would expect theobserved parity-violating asymmetries to be evenly

distributed in sign; in fact, the statistically significantasymmetries all have the same sign. Theories have beenextended to account for this. It is clear that thesemeasurements have fundamentally altered ourunderstanding of compound-nucleus reaction mechanisms.Further measurements will help elucidate the problem andextend our knowledge of time-reversal invariance.

With the new Neutral Meson Spectrometer (NMS)under construction, the venerable rc() Spectrometer isnearing the end of its useful life at LAMPF. However, itstill played an important role in the pion physics programduring 1991. Measurements of pion single chargeexchange from aligned Ho allowed the neutrondistribution in this nucleus to be determined. These datashow that the neutron deformation is significantly les.;than the charge (proton) deformation. The 71°Spectrometer was aiso used to set an upper limit for theemission of neutral pions in spontaneous fission.

Construction and testing continued on several largeexperiments. These include MEGA (an acronym standingfor Muon decays into an Electron and a G_Anima ray I.which will search for the lepton-familv-numbernonconserving decay [i+ —> e+y; Liquid ScintillatorNeutrino Detector (LSND), which will search with highsensitivity for neutrino oscillations (which is anotherprocess that does not conserve lepton family number): andan experiment designed to make ultra-high-precisionmeasurements on the ground stale of muonium. In thecourse of commissioning the MEGA detector, it wasleali/ed that the apparatus could also be used to measurethe Michel parameter p in normal muon decay withimproved accuracy. The Michel parameter provides asensitive test of the V-A nature of the weak interaction.MHGA should be ready to he»in taking data in 1992.

Progress at LflMPF

while LSND and the muonium experiment will follow inthe next year. An experimental search tor the spontaneousconversion of muonium to antimuonium is nowcomplete. This is a process that is allowed in severalextensions to the Standard Model. The data from thisexperiment shovvod no evidence for this spontaneousconversion; it showed that the coupling constant for thisprocess must be significantly smaller than the Fermicoupling constant.

Work at the High Resolution Atomic Beam Facility(HIRAB) centered on multiphoton detachment of H~,multiphoton absorption in H . and the study of singlephoton detachment in electric fields. New measurementsat the stopped rnuon channel (SMC) were used to developa new technique for materials science research withmuons. muon level-crossing resonance (|iLCR). Here onescans a longitudinal magnetic field to find those values atwhich resonant transfer of muon polarization toneighboring nuclei takes place. The main feature of this

Foreword

method is that it can be performed in an integral mode sothat the duty factor of LAMPF is not a disadvantage.Appropriate beam tunes were developed and (iLCR signalswere observed.

The CYGNUS extensive air-shower array continuedto lake data and set the most sensitive upper limits to datefor emission of ullra-high-energy gamma rays from pointsources. Studies of the response of a 24-foot-diameierwater Cerenkov detector indicate that this technique can beused to achieve markedly better angular resolution.

The diversity and breadth of the physics program atLAMPF contributes to a vital, world-class facility. Newexperimental capabilities, including MEGA, the NeutralMeson Spectrometer, LSND. and the facility for precisionstudies of muonium assure exciting physics results in thefuture. As new directions for the program continue toemerge, we are confident that first-class facilities at theintensity frontier that is LAMPF's hallmark will continueto *rve our User community in the vears ahead.

Peter D. BarnesDirector of LAMPF

Progress at LHMPFContents

Contents

Experimental Areas XI

LAMPF Users Group »•//Twenty-Fifth Annual Meeting 3Committees 4Workshops oVisitors Center 8Newsmakers 9

Research 12Nuclear and Particle Physics 15

EXPERIMENT 998 - EPICS

Coincidence measurement ol' 4He(7i.7i'l)p 15


The nature of T< states observed in DCX on medium-muss nuclei 17

EXPERIMENT 1203 - HRS

Pion production at small angles for PILAC J9

EXPERIMENT 1183 -LANSCE

The study of parity and time reversal symmetry violation in the compound nucleus 21

EXPERIMENT 899 - LEP

A measurement of the neutron deformation of 'fi-M-lo by pion single charge exchange 23

EXPERIMENT 225 - Neutrino A

Search for the e.xoiic decay f.t+ —> e+v cVp 26


Experimental Mudy of neutrino prop 'ilies 2'J

Progress at LflMPFContents


Search for neutrino oscillations with high sensitivity in the appearancechannels vu —> ve and v^ —* v c 33

EXPERIMENT 881 - NTOF

Measurement of the spin-longitudinal and spin-transverse nuclear responses in the'-C(p,n) and 4()Ca(p,n) reactions at 495 MeV 36


Cal ibration of the NTOF detector system for polari metry 40

EXPERIMENTS 876, 1072, AND 1234 - OPPIS

Nucleon-nucleon experiments using the Line B facility 44

EXPERIMENT 1126-P3East4He(Jt+,pp)pn reaction at 500 MeV 48

EXPERIMENT 1129 - P3East

Search for neutral pions from the spontaneous fission of —">-Cf 52

EXPERIMENT 1190 - P3West

Pion-proton partial total cross sections from 60 to 200 MeV 54

EXPERIMENT 969 - SMC

MEGA: Search for the rare decay )n+ —» e+y 57


Ultra high precision measurements on muonium ground state:hyperfine structure and muon magnetic moment 63


New search for the spontaneous conversion of muonium to antimuonium 67

EXPERIMENT 1240-SMC

RHO: Measurement of the Michel parameter p with the MEGA positron spectrometer 68

EXPERIMENT 1208 - WNR

Neutron-proton bremsstruhlung studies at LAMPF/WNR 70

EXPERIMENT 2N0030 - WNR7Li activation measurements at 795 MeV 71

EXPERIMENT 4N0015 - WNR

Studies of Gamow-Teller and giant resonance excitation in the (n,p) reaction at the WNR 73

Astrophysics 75CYGNUS Hxperimerit 75

Progress at LBMPFContents

Atomic and Molecular Physics 79EXPERIMENTS 1121 AND 1127 - HIRAB

Relativistic H~ spectroscopy 79

Materials Science 84EXPERIMENT 1235

Muon level-crossing resonance spectroscopy 84

Radiation Effects 86Radiation damage and radiation effects to materials 86

Radioisotope Production 8HINC-1 1 radioisotope production activities 8N

Theory 91Pion-induced elastic and inelastic scattering above the 3.3 resonance 91Production of r\ mesons by pions 94

Report of the T-5 theoretical group 97

MP-Di vision Publications 108

20Facility Development

Accelerator computer control systemA radioactive beam facility - a new initiative.Development of polarized 7Li target material.LAMPF Data Analysis Center (DAC)RF system development

24

27

30

32

Environment, Safety, and Health 136

Accelerator Operat ions 142

Mi lestones 146

Appendixes 156Appendix A:

Experiments run in 1991 158

Appendix B:New proposals during 1991 160

Appendix C:LAMPK visitors during 1991 ](o

Information for Contributors 171

Progress at LRMPFExperimental Hreas

Experimental Areas

Neutrino0 10 20 30 Detector

BEAMSProtons or H+

Polarized protons or H"

Pions or Muons

Neutrinos

Neutrons

High Intensity Protons

High Intensity H" (for LANSCE)

Polarized H"

Low-energy Pion Channel

High-energy Pion Channel

Stopped-muon Channel

Neutron Beam Channel

SPECTROMETERS

EPICS Energetic Pion Channel and Spectrometer

High-resolution Spectrometer

Medium-resolution Spectrometer

Time-of-flight Isochronous Spectrometer

HRS

MRS

TOFI

FACILITIES

HIRAB

NOTF

ISORAD

LANSCE

WNR

High-resolution Atomic Beam Facility

Neutron Time-of-flight Facility

Isotope Production and Radiation Effects

Los Alamos Neutron Scattering Center

Weapons Neutron Research Facility

LAMPF Users Group

TWENTY-FIFTH ANNUAL MEETING

COMMITTEES

WORKSHOPS

VISITORS CENTER

NEWSMAKERS

LflMPF Users Group

Twenty-fifth annual meeting

Rnnual Meeting

The Twenty-Fifth Annual Meeting of the LAMPFUsers Group, Inc., was held in Los Alamos on August19-20, 1991, with 125 attendees. Chairman JacoboRapaport (Ohio University) presided at the first session,which included the following presentations:

"Welcome," Frederick Morse, Associate Director forResearch;

"Report from Washington," Sherman Fivozinsky,Department of Energy;

"Status of LAMPF," James Bradbury, Deputy Directorof LAMPF;

"Future Directions for LAMPF," Peter Barnes, Directorof LAMPF; and

"Report from the Users Group," Jacobo Rapaport (OhioUniversity).

The Louis Rosen Prize was presented to Bjorn EckartMatthias (Yale University) for his thesis entitled,"A NewSearch for Conversion of Muonium to Antimuonium."

The afternoon session was conducted by incomingChairman David Ernst (Texas A&M University). Thefollowing talks were given during *he session:

"PILAC Physics," Robert Chrien (BrookhavenNational Laboratory);

"Status on Neutrino Physics," Paul Langacker(University of Pennsylvania);

"Radioactive Beam Physics," Richard Casten(Brookhaven National Laboratory);

"View from the Director's Office," Sig Hecker (LosAlamos);

"Computer Upgrades and MBD Replacement for DataAcquisition," Michael Oothoudt (Los Alamos).

On the second day of the meeting the session waschaired by the new Chairman-Elect R. Jerry Peterson(University of Colorado). The following talks were givenduring the session:

"The Scruncher: Overview, Status, and Prospects,"Barry Ritchie (Arizona State University);

"Parity Violation in Neutron Resonances," GaryMitchell (North Carolina State University):

"Isovector Spin Response from (p,n) Reaction at500 MeV," Terry Taddeucci (Los Alamos).

During the remainder of the day, various workinggroups met.

1RMPF Users GroupCommittees

Committees

Board of Directors

The Board of Directors comprises a Liaison Officerand seven members elected by the LAMPF Users Group.Inc.. whose interests they represent and promote. Theyconcern themselves with LAMPF programs, policies,future plans, and especially with how users are treated atL A V J P F . The Board also nominates new members foi theProgram Advisory Committee (PAC). Users shouldaddress problems and suggestions to individual BoardMembers.

The 1991 membership and term expiration dates arelisted below.

James Bradbury(Liaison Officer)Los Alamos

Terms Expiring in 1991Robert McKeownCalifornia Institute of Technology

Harni} SpinkaArgonne National Laboratory

Evan SugarbakerOhio State University

Terms Expiring in 1992James McCarthyUniversity of Virginia

Jacobo RapaportOhio University

Susan SeestromLos Alamos

Terms Expiring in 1993David ErnstTexas A&M University

Experimental Facilities Panel

The Experimental Facilities Panel (EFP) providestechnical recommendations to the Board of Directors andLAMPF management about the development ofexperimental facilities and support activities. Thechairman of the Board of Directors will also act aschairman of the EFP. The EFP consists of not more thanfifteen (15) members, each of whom serve for two (2)years, chosen so thai approximately half of the panelconsists of continuing members each year, and so themajor experimental facilities and beam channels arerepresented. The duties of the EFP members are to: (I)solicit information from the Users and from LAMPF staffon problems, suggested improvements, and futuredevelopments; (2) disseminate such information to theUsers: (3) report on User activities, problems, andsuggestions at meetings of the EFP: and (4) chair workinggroup meetings at the annual Users Meeting. The EFPwill meet at least twice a year, and members of the Board

LRMPF Users GroupCommittees

of Directors and the Liaison Officer are to be membersex offieio.

Members and term expiration dates are listed below.

Terms Expiring in 1992r. Todd Baker - HRSUniversity of Georgia

Byron Dieterle - Neutrino FacilitiesUniversity of New Mexico

Gary Hogan - SMCLos Alamos

James Knudson - Computer FacilitiesLos Alamos

Terms Expiring in 1993June Matthews - P-̂Massachusetts Institute of Technology

Barry Ritchie - LEPArizona State University

Gerald Hoffman - Polarized TargetUniversity of Texas

John Ullmann - NPLLos Alamos

Christopher Morris - EPICSLos Alamos

Terry Taddeucci - NTOFLos Alamos

Terms Expiring in 1994Peter Haustein - Nuclear ChemistryBrookhaven National Laboratory

LflMPF Users GroupWorkshops

Workshops

LAMPF Workshops and meetings in 1991:

NMS Collaboration MeetingJanuary 11, 1991

Accelerator-Based Low-EnergyNeutrino Physics WorkshopJanuary 13-14, 1991

Program Advisory Committee (PAC)January 14-17, 1991

PILAC Optics MeetingFebruary 7, 1991

PILAC Users Group MeetingFebruarys, 1991

LSND Group MeetingMarch 1-2, 1991

MEGA Collaboration MeetingMarch 4-5, 1991

PILAC Cavity/RF Review WorkshopMarch 11-12, 1991

MILAGRO Collaboration Meeting(Santa Cruz, California)March 25, 1991

CYGNUS Collaboration Meeting(Santa Cruz, California)March 26-27, 1991

NMS Collaboration MeetingMay 17, 1991

LSND Group MeetingMay 20-21, 1991

Fourth Conference on theIntersections Between Particle andNuclear Physics(Tucson, Arizona)May 24-29, 1991

CYGNUS Collaboration MeetingJune 10-11, 1991

MEGA Collaboration MeetingJune 10-11, 1991

LSND Group MeetingJuly 17-18, 1991

PILAC Optics WorkshopAugust 12-13, 1991

LAMPF Users MeetingAugust 19-20, 1991

LflMPF Users GroupUJorkshops

LSND Group MeetingNovember 15-16, 1991

RHO Collaboration MeetingDecember 13-14, 1991

The following LAMPF workshops are scheduled in 1992:

Program Advisory Committee (PAC)January 14-17, 1992

N-N and N-Nucleus ScatteringJanuary 13-14, 1992

LAMPF Users MeetingAugust 17-18, 1992

Program Advisory Committee (PAC)August 18-21, 1992

PILAC Users Group MeetingAugust 19-20, 1991

Program Advisory Committee (PAC)August 20-23, 1991

MEGA Collaboration Meeting(Blacksburg, Virginia)September 8-9, 1991

PILAC Users Group ExecutiveMeetingSeptember 27, 1991

PILAC Superconducting CavityWorkshopOctober 3-5, 1991

PILAC Users Group Meeting(Lansing, Michigan)October 24, 1991

NMS Collaboration MeetingNovember 15, 1991

LflMPF Users GroupUisitors Center

Visitors Center

During this report period, 544 research guests workedon LAMPF-related activities or participated inexperiments at LAMPF; of these 241 were foreignvisitors.

LAMPF Users Group Membership

MembershipNon-LaboratoryLos Alamos National Laboratory

TOTAL

Institutional DistributionMembership by Institutions

Los Alamos National LaboratoryNational or Government LaboratoriesU.S. Universities

Number of InstitutionsNational or Government LaboratoriesU.S. UniversitiesIndustryForeignHospitalsNonaffiliated.

850242

1,092

227

107

473

IndustryForeignHospitalsNonaffiliated

TOTAL

26209

644

1.092

TOTAL_

32

133

24

116

5

5315

Regional BreakdownEast

Pennsylvania, New Jersey, Delaware,Washington DC, Massachusetts,New York, Connecticut, Vermont,Rhode Island, New Hampshire,Maine

Midwest

Ohio, Missouri, Kansas, Indiana,Wisconsin, Michigan, Illinois,North Dakota, South Dakota,Nebraska, Iowa, Minnesota 11.6%

SouthMaryland, Virginia, Tennessee,Arkansas , West Virginia, Kentucky,North Carolina, Alabama, Mississippi ,Louisiana, Georgia, Forida,South Carolina 11 XW<

Southwest, Mountain

Montana, Idaho, Utah, Wyoming.Arizona, Colorado, New Mexico(excluding Los Alamos), Oklahoma,Texas

WestAlaska, Hawaii, Nevada, Washington,Oregon, California

Foreign_

Los Alamos National Laboratory

. 14.57r

9.37r

19.7%

21.47r

Progress at LflMPF

Newsmakers

Newsmakers

Barnes Appointed Director of LAMPF,MP-Division Leader, and Program Director forNuclear and Particle Physics for LANL

Peter Barnes is the new director of the Los AlamosMeson Physics Facility and leader of the Medium EnergyPhysics Division (MP). He also will serve as programdirector for nuclear and particle physics. Barnes, aprofessor of physics at Carnegie-Mellon University inPittsburgh since 1968, replaced Ed Knapp, who retired.

The appointment is actually a return to Los Alamosfor Barnes. He was a postdoctoral fellow in theLaboratory's physics division from 1966-68, and took ayear's leave from Carnegie-Mellon during the 1973-74academic year to serve as a visiting staff member atLAMPF.

Barnes has written, edited, or coauthored more than100 scholarly papers or conference proceedings in the fieldof nuclear physics. After earning his Ph.D. at Yale,Barnes received a Fullbright Award and a NATOFellowship in 1965 and spent 1964-66 at the Niels BohrInstitute in Copenhagen, Denmark. He received a SeniorFullbright Award in 1978 and spent the 1978-79 academicyear as a visiting scientist at the Linear ElectronAccelerator Facility of the Centre Etude Nucleaire, Saclay,Gif-sur-Yvette, Paris.

Barnes is a fellow of the American Physical Society,Sigma Xi, the American Association for the Advancementof Science, and the New York Academy of Sciences. Hehas served as a member of numerous boards and advisorycommittees in physics, including past service on theLAMPF PAC (1976-78) and twice on the LAMPF UsersGroup Board of Directors (1972-74 and 1983-86).

Peter D. Barnes (photo by Fred Rick).

Reorganization at LAMPFM. Hoehn, E. Hoffman, J. Little Assume NewDuties

In May 1991 Earl Hoffman became Deputy DivisionLeader for Operations; a second slot, Deputy Division forResearch, remained unfilled. Earl was most recentlyGroup Leader of MP-6. He assumed the position whenGroups MP-1 and MP-2 were consolidated in 1988.

In June 1991 Martha Hoehn succeeded Earl Hoffmanas Group Leader of MP-6.

Jim Little has been long-time Deputy Group Leaderof MP-1 and has recently served in MP-DO in the PSRProgram Office. On Don Cochran's retirement. Jimbecame Acting MP-Division Safety Officer. The neworganization combines Safety with other Support

Progress at LHMPFNewsmakers

Services, including User Support and the LAMPFProperty Office; it is designated Safety and SupportServices Group MP-i, and Jim Little is Group Leader.

A new Program Manager for Environment. Safety,and Health (ES&H), has yet to be selected to complete thenew organization.

Louis Rosen Prize

Bjoin Eckart Matthias received the Ninth AnnualLouis Rosen Prize at the recent annual meeting of theLAMPF Users Group. August 19-20. 1991. The LouisRosen Prize is presented annually for the mostoutstanding Ph.D. thesis with the research work havingbeen done at LAMPF. The prize consists of a plaque and$1,000.

Matthias' thesis is titled "A New Search forConversion of Muonium to Antimuonium" and was doneunder the supervision of Vernon Hughes of Yale.

Matthias spent the years 1986 to 1991 at Los Alamosworking with the Yale group on several muonexperiments. He was awarded his Ph.D. from Yale inFebruary 1991. The results of his thesis work haveappeared in Phys. Rev. Lett. 66, 2716 (1991).

The work used a new technique to search for theconversion of muonium to antimuonium, a process thatviolates lepton-number conservation and is thus forbiddenin the standard model. Matthias stopped muonium in apowder, allowed it to diffuse into the neighboringvacuum, and then looked for the antimuonium decayproducts of an energetic electron and an atomic positron incoincidence. A new upper limit on the conversionprobability per atom of 6.5 x 10""^ was set. This

translates into an effective coupling constant for theconversion in a (V-A) theory of G < 0.16 Gp. which isthe order of what occurs in some contemporary theories.

Matthias has taken a postdoctoral position at theUniversity of Heidelberg working with Prof. Gisbert zuPutlitz. They have proposed utilizing the same techniqueas was used at LAMPF to construct an even moresensitive muonium to antimuonium conversionexperiment at PSI.

Sherman Fairchild Distinguished ScholarG. T. Garvey

Gerald T. Garvey has been selected as a ShermanFairchild Distinguished Scholar by the California Instituteof Technology. The Program brings renowred scientistsand scholars to Caltech to provide the faculty and studentsthe opportunity to interact with world leaders in variousfields. The emphasis in the program is on giving facultyand students exposure to Fairchild Scholars in all academicdivisions - through discussions, seminars, lectures, andresearch - and establishing a forum for the exchange ofideas among Fairchild Scholars, Caltech faculty andstudents, and industry. Appointments are usually fromthree to nine months during the academic year.

Garvey, formerly Director of LAMPF. is a LosAlamos National Laboratory Senior Fellow whoparticipates in the LAMPF research program as a memberof the MP Division's Nuclear and Particle Physics Group(MP-4). His current research interests are the properties ofneutrinos, quark structure functions, and parity violationin compound-nucleus reactions.

10

Research

NUCLEAR AND PARTICLE PHYSICS

ASTROPHYSICS

ATOMIC AND MOLECULAR PHYSICS

MATERIALS SCIENCE

RADIATION EFFECTS

RADIOISOTOPE PRODUCTION

THEORY

MP-DIVISION PUBLICATIONS

ResearchNuclear and Particle Physics

Nuclear and Particle Physics


Coincidence measurement of 4He(7T,7i't)pINSTITUTIONS: Univ. of Minnesota, Los Alamos National Laboratory, New Mexico State Univ.

PARTICIPANTS: J. L. Langenbrunner, M. K. Jones, D. Dehnhard (spokesperson), C. L. Morris (spokesperson), andW. R. Gibbs

Angular correlation functions for the exclusivereaction 4He(7i,7i'p)T were measured in LAMPF Exp. 998using the Energetic Pion Channel and Spectrometer(EPICS). The 7i-proton coincidence data have beenpublished by Jones et al. ' We have reanalyzed theexperimental data and extracted 7t-lriton coincidences, i.e.,4He(Ji,7i'i)p for tritons emitted in the forward hemisphere.The triton-coincidence data correspond to protons emittedin the backward direction near 6p ' ' = 180°, where thevariable 6p ' ' is the proton emission angle in the cm.system of the recoiling mass 4 system. Therefore, thesedata augment the 4He(Ji,7i'p)T angular correlation data ofRef. 1 in the backward hemisphere. A description of theexperiment can be found in Ref. 1.

Previous to this report for 4He(jt± , i t± ' t )p, tritonsdetected in coincidence with scattered pions have beenidentified only for the ^Cdt*,?!*'!) reaction.2 Thestatistics reported in Ref. 2 are poor and no attempt wasmade to model the triton-knockout. The target 4He is aself-conjugate, spin- and isospin-zero nucleus. Ourapproach of analyzing the data for both protons and tritonsin this coincidence experiment provides us with data forthe angular correlation function spanning a large fractionof the reaction plane. This gives us the opportunity totake full advantage of the strong isospin dependence of thepion probe at 180 MeV, where the reaction is dominatedby the P33 resonance. For example, we expect largeryields for triton-knockout with n~ compared to TI+

because the K~ probe interacts preferably with the twoneutrons of the triton, whereas the p + interacts preferablywith the triton's single proton.

The most striking feature of the data is easily seen inthe isospin asymmetry A, as defined in the equation

0(JI+,7T.+'p) - O(7I ,7t 'p)-

. ,rtC.nr 0(JI+,7T.+p) -Aj(Wp ) =

( + + ' )(1)

G(7C\JI+'p) + O(7C~.JI~'p)

an example of which is shown in Fig. 1. If the reactionproceeds through quasifree 7t-proton scattering, then thefree pion-nucleon ratio o(n+,p)/o(7C~,p) of 9 should apply,assuming the reaction involves only the P33 rc-nucleonresonance. In that case, A;(9p' ') will be equal to +0.8independent of the scattering angles of the pion andproton. In the case where the nucleus is excited to aresonance state of pure isospin, Aj(6p ) will also beindependent of the scattering angles, but its value will beequal to zero. We have found that the experimentalisospin asymmetry Aj(8p' ') varies strongly with Gp

from near +1.0 in the kinematic region of quasifree-protonknockout, to -0.6 in the kinematic region of quasifree-triton knockout. :

We hypothesize that the 4He(Jt,Jt 'p)T reactioninvolves the sum of. the amplitudes for these twoprocesses: direct proton knockout with a maximum near6p ' ' = 0°, and direct-triton knockout, which results in aproton emitted primarily near Gp' ' = 180°. The solidline in Fig. 1 shows our preliminary calculation using amodel that assumes the coherent knockout of protons andtritons (with the other being a spectator). In this model,all momenta are determined by the conditions that the sumof the Fermi momenta of proton and triton are zero andthat the final momentum of the unstruck particle is equalto its initial Fermi momentum. Final-slate interactionshave not been included in the two-amplitude calculation.In another model (THREEDEE, Ref. 3), with proton-knockout considered alone, Aj(6p' ) is found to be nearlyisotropic (between +0.8 and +0.6). The dashed line is iheTHREEDEE model calculation, presented in Ref. 1.

15


Deviation from isotropy in that model comes from n-nucleon s-wave interaction and nuclear distortions.-'

We conclude that triton-knockout is essential to ourunderstanding of the data, but existing reaction modelshave had only limited success in quantitativelyreproducing the data. We are planning to measure angularcorrelation functions for exclusive reactions (ji.jt'X) on•'He and 4He, (where X = p, d, t, ...) in the approvedLAMPF Exp. 1216. We will take data as a function ofexcitation energy and momentum transfer (as inExp. 998). We will increase the pion-bombarding energyabove the P33 resonance, to 300 MeV, where the 71-nucleon cross-section ratio decreases significantly from thevalue of 9 near 180 MeV. We expect that our data willreflect the relative importance of different reactionmechanisms for pion-induced knockout of particles Xfrom -̂ He, and 4He. This will provide us withinformation on the nature of pion-nucleus interactions,and possibly on the nature of the target nucleus wavefunctions.

References

1. M. K. Jones, D. Dehnhard, S. K. Nanda, S. Sterbenz,C. L. Morris, M. Plum et al., Phys. Rev. C 42,R807 (1990); Christopher L. Morris, Bull. Am.Phys. Sot: 33, 1093 (1988); M. K. Jones, "PionElastic Scattering and the (7t,7t'p) Reaction on 4He inthe A3 3 Region," Ph.D. thesis, University ofMinnesota, Los Alamos National Laboratory reportLA-12015-T (March 1991); and Phys. Rev. C 46, 52(1992).

Ftg. 1. The isospin asymmetry (as defined in the text) isgiven for the *He(K-,K~'p) reaction as a function ofQp '. The data were taken at Tn = 180 MeV, and 6n =30°. The two-amplitude calculation (solid line)qualitatively describes the data and shows the importance

C tfi

of direct-triton knockout for 0p ' ~ 180°. The dashedline represents the lsj/2 nucleon knockout modelcalculation1 with THREEDEE.3 That model includes onlyproton knockout and Aj is nearly isoiropic with a value ofAi(6Cp"'') between 0.6 and 0.8.

2. R. J. Ellis, H. J. Ziock, K. O. H. Ziock, Y. Tzeng,J. Arvieux, R. Corfu et al., Phys. Rev. C 26, 1544(1982).

3. N. S. Chant, computer code "THREEDEE;" see also N.S. Chant, L. Rees, and P. G. Roos, Phys. Rev. Lett.48, 1784 (1982); L. Rees, N. S. Chant, and P. G.Roos, Phys. Rev. C 26, 1580 (1982).

16



The nature of T< states observed in DCX on medium-massnucleiINSTITUTIONS: Univ. of Pennsylvania, Univ. of New Mexico

PARTICIPANTS: M. A. Kagarlis (spokesperson), D. A. Smith (spokesperson), A. Williams, P. Hui, S. Loe, H. T. Fortune(spokesperson), and J. V. Urbina

Preliminary measurements of DCX cross sections inthe reaction 9 3Nb(Tt+ , jr)9 3Tc (Ref. 1) revealed at leastone strong state just below the double isobaric analogstate (DIAS). Since the DIAS is the lowest lying isobaricstate that can be reached from a target via sequential DCX,this new state was believed to differ from the target groundstate by one unit of isospin. Similar states were observedin the reactions 56Fe(7t+ ,jr)56Ni and l38Ba(7i+,rt~) l38Ca(Ref. 2). We shall refer to these states as the T< states.The T< states above were observed accidentally at oneincoming pion energy at EPICS, with the focal plane ofthe spectrometer centered far from the energy of thesestates.

The mechanism by which the T< states are occupiedhas not been studied; the objective of Exp. 1207 was tomeasure the DCX cross sections of these states in93Nb(7t+,Ji~) and 56Fe(Ji+,Ji~) at three incoming pionenergies. By studying the excitation function, one couldlearn more about the reaction mechanism that allows forthe populating of these states via DCX. In particular, twobehaviors have been widely observed in the past in DCXexperiments.3-4 One characteristic behavior, believed tobe the signature of non-spin-flip sequential DCX, is theshape of the excitation function in populating the DIAS.Aside from small deviations, most likely due to nuclearstructure, excitation functions obtained frommeasurements of the DIAS are more or lessmonotonically increasing in the range of TK = 100 to300 MeV. In contrast, excitation functions obtained bymeasurements of DCX cross sections to the residualground state reveal a strong peak near the A33 resonance(near 164 MeV) and fall rapidly at higher pion energies.This behavior was thought to be characteristic of a one-

step resonance excitation of a A in the nucleus followedby its subsequent decay. At present, however, research inprogress5 on the effect of sequential spin-flip seems to besuggesting that this resonant behavior may be explainedpartly or fully by sequential spin-flip. Results areexpected soon, which will shed more light on this openquestion.

In June of 1991, the first part of Exp. 1207 wascompleted; measurements of cross sections were taken atTK = 292, 230, and 164 MeV at 5° at EPICS. Thepreliminary results for the 292-MeV spectrum areconsistent with the measurements reported in Ref. 1. Inaddition, one new T< was resolved at 230 MeV (betterthan a three-sigma peak) and the IAS x GR previouslymeasured at 292 MeV (Refs. 6 and 7) was measured at 230MeV as well. We expect to finish our analysis and reportour results for 9 3 N b shortly. The second part ofExp. 1207, measurements of DCX cross sections in thereaction 56Fe(7t+,n~), will run at EPICS at a later time.

References

l . C . F. Moore, K. Johnson, G. P. Kahrimanis, J.McDonald, M. Snell, H. J. Ward et al.. Pins. Rev.C44 , 2209 (1991).

2. J. M. O'Donnell, H. T. Fortune, J. D. Silk, S.Mordechai, C. L. Morris, J. D. Zumbro et al.. "T =13 Double Isobaric Analog State in 138Ce via Pion-Induced Double Charge Exchange" (in preparation,1992).

17


3. H. T. Fortune, S. Mordechai, R. Gilinan, K. Dhuga, 6. S. Mordechai, H. T. Fortune, J. M. O'Donnell, G.J. D. Zumbro. G. R. Burleson et al., Phys. Rev. C Liu, M. Burlein, A. H. Wuosmaa et al., Phys. Rev.35, 1151 (1987). C40, 850(1989).

4. R. Gilman, H. T. Fortune, M. B. Johnson, E. R. 7. J. M. O'Donnell, H. T. Fortune, J. D. Silk, S.Siciliano, H. Toki, and A. Wirzba, Phys. Rev. C32, Mordechai, C. L. Morris, J. D. Zumbro el al., Phys.349(1985). Rev. C41, 202 (1990).

5. M. A. Kagarlis, "Spin-Flip Effects in Pion-NucleusInteractions," Ph.D. thesis, University ofPennsylvania (1992).

18


EXPERIMENT 1203 - HRS

Pion production at small angles for PILACINSTITUTIONS: Univ. of Minnesota, Univ. of Houston, Los Alamos National Laboratory

PARTICIPANTS: J. L. Langenbrunner, M. Barakat, E. Hungerford, C. Pillai (spokesperson), H. A. Thiessen, N. Tanaka(spokesperson), L. Rybarcyk, D. B. Barlow, K. W. Jones, C. L. Morris, J. McClelland, and R. D.Werbeck

There has been increased interest to build a super-conducting accelerator for pions (PILAC) at LAMPF.'Significant increases in the accelerated flux can beachieved by collecting and accelerating pions produced nearzero degrees with respect to the primary proton beam.The pion-production cross section peaks at forward angles.However, with few exceptions, there are no data for Jt+

and Jt~ production at very small angles.

The present data were obtained using the HighResolution Spectrometer (HRS) at the Clinton P.Anderson Meson Physics Facility (LAMPF). The energyof the incident proton beam was 800 MeV. The targetsused are of the type that are considered for use in PILAC.including different forms of natural carbon ("ATJ" and"Pyrolytic"), and copper. The beam flux was monitoredby a pair of ion chambers and by the beam-linepolarimeter (located a few meters upstream of the target).The beam monitors were calibrated by measuring the crosssection for 'H(p,p) elastic scattering at laboratory anglesof 5, 7.5, 10, 15, and 20 degrees. Because the ionchambers could not be used to integrate beam formeasurements at angles less than 5 degrees, the data hereinuse the polarimeter calibration only. We report a standarddeviation of 3.5% in the comparison of the ion chambersand the polarimeter. In order to determine the solid angle,we normalized our results to 'H(p.p) differential crosssections determined from a global phase-shift analysis ofArndt.- The differential cross sections from the programSAID for the 'H(p,p) reaction are reliable to within 5%and the total systematic uncertainty in our calibrationprocedure is 8%. Particle identification was achieved byspecifying the time-of-flight of particles through the HRSspectrometer and the pulse-height response of scintillatordetector S2 as in the usual HRS setup.-1 We estimate that

systematic error consists primarily from our normalizationof the product of beam flux and solid angle using ' H(p,p)cross sections and LCP02 polarimeter. We estimate thiserror to be ± 8 % . Error in target thickness isapproximately 4% for our measurements and the error inmomentum bite is about 1%. Statistical error (includingthe effect of background subtraction) is given in the tablesand is generally less than 4%. We expect our results fordouble-differential cross sections at angles of 5 degrees andlarger to be accurate within ±10%. In the case of 0 and 3degrees, we used the normalization the same as reported inthe previous section. However, because our calibrationwas made at angles of 5 degrees and larger, it is notknown if the solid angle changes slightly forward of 5degrees. We estimate our total error at 0 and 3 degrees tobe ±15%. Details of this experiment are given in Ref. 4.

The spectrometer was used to select the energy of thepions (between 250 and 550 MeV) at laboratory angles of0. 3, 5, 7, 10, 15, and 20 degrees. Figures 1 and 2 showthe data for pion production as a function of spectrometerangle; lines connect data of constant pion energy. Thepresent data complement the previous data of Refs. 5 and6 with measurements of the Jt+ and jr~ production crosssection by 800-MeV protons incident on carbon andcopper targets. In the cases of overlap with the previousmeasurements, there is good agreement. Aspects of thisdata that take into account multiple scattering andabsorption as a function of target thickness are still underevaluation.

We have fit these data with a slowly varying functionof angle near zero degrees where the experimentaldifficulties are most severe. Based on that analysis. 365 ±15 MeV is the optimum energy for injection of JI+ and330 ± 15 MeV is the optimum injection energy for it".


- f r - 250 MeV

- • - 300 MeV

- - > 350 MeV

- ¥ - 375 MeV

- * - 400 MeV

-rir- 425 MeV

- 0 - 450 MeV

- O - 500 MeV

- * - 550 MeV

4 8 12 16

Lab Angle (deg)20

Fig. I. Differential cross sections (flb/MeV/sr)for Jt* andK~ production from carbon as a function of HRS anglesetting. Lines connect the data at constant pion energy.

-fr- 250 MeV

- • - 300 MeV

- - 350 MeV

- * - 375 MeV

-A- 400 MeV

-IT- 425 MeV

- 0 ~ 450 MeV

550 MeV

4 8 12 16

Lab Angle (deg)20

Fig. 2. Differential cross sections (fib/MeV/sr)for 7T+ and

K~ production from copper as a function of HRS angle

setting. Lines connect the data at constant pion energy.

taking into consideration survival fraction and the requiredphase space. Details of the analysis and the constantsused in the fits to the angular distributions are given inRef. 7.

This work is dedicated to the memory of our friendand colleague, Nobuyuki Tanaka, who died unexpectedlyduring the course of this project. His skills, support, andinsight were the motivation for these experiments.Nobuyuki led the teams of people building and designingthe HRS.

References

1. H. A. Thiessen, PJLAC Technical Note No. 13. LosAlamos National Laboratory document LA-UR-91-869(1991).

2. B. Zeidman, Los Alamos Scientific Laboratory reportLA-4773-MS, Part 1 (1977); K.W. Jones. Ph.D.

thesis, Los Alamos National Laboratory report LA-10064-T(1984).

3. R.A. Arndt, J. S. Hyslop III, and L. D. Roper. Phys.Rev. D35, 128 (1987). A. J. Simon and M. W.McNaughton estimate a 5% uncertainty in the'H(p.p) cross section derived from this phase-shiftanalysis of Arndt as the result of continuing researchto improve the basis data set.

4. ]. L. Langenbrunner and C. Pillai, PILAC TechnicalNote No. 20, Los Alamos National Laboratorydocument LA-UR-91-1268 (1991).

5. D. B. Barlow, B. M. K. Nefkins. C. T. Pillai, and K.W. Jones, Nucl. lustrum. Methods A 271, 471(1988).

6. P. Denes, B. D. Dieterle. D. M. Wolfe. T. Bowles.T. Dombeck, J. E. Simmons. T. S. Bhatia, G. Glass,and W. B. Tippens, Phys. Rev. C27 . 1339 (N83).

7. H. A. Thiessen, PILAC Technical Note No. 27. LosAlamos National Laboratory document LA-UR-91-2022(1991).

20


EXPERIMENT 1183 - LANSCE

The study of parity and time reversal symmetry violationin the compound nucleusINSTITUTIONS: Los Alamos National Laboratory, Duke Univ., North Carolina State Univ., Joint Institute for Nuclear

Research (JINR, Russia), KEK (Japan), TRIUMF, Technical Univ. of Delft (The Netherlands)

PARTICIPANTS: C. D. Bowman, J. D. Bowman (spokesperson), C. M. Frankle, J. Knudson, R. Mortensen, S.Penttila, S. J. Seestrom, S. A. Wender, Yi-Fen Yen, S. H. Yoo, V. W. Yuan, C. R. Gould, G. E.Mitchell, N. R. Roberson, E. I. Sharapov, Yu. Popov, A. Masaike, Y. Masuda, Y. Matsuda, H. M.Shimizu, S. Takahashi, P. P. Deihaij, and H. Postma

The aim of the work is to study the violation offundamental symmetries such as time reversal and parityusing the compound nucleus as a laboratory. Highlyexcited nuclear states are formed when epithermal neutronsare captured by nuclear targets. Symmetry tests can becarried out by observing the dependence of neutrontransmission or reactions on neutron spin, neutronmomentum, and target spin. The Los Alamos ProtonStorage Ring and Spallation Neutron Source provides anintense source of pulsed neutrons. These neutrons arepolarized by passing them through a "spin filter"consisting of a cell of dynamically polarized protons.

We have made sensitive measurements of ParityViolation in 238U (Ref. I) and 232Th (Ref. 2). Threestates in 238U and seven states in 232Th showed parity-violating asymmetries with a statistical significancegreater than 2.5 standard deviations. Since the wavefunctions of the compound nuclear states consist of linearcombinations of 105 to 106 single-particle configurationsit is to be expected that observables will have a statisticalcharacter, and the statistical model of the compoundnucleus treats observables as random variables. We havedeveloped techniques to extract the mean squared mixing,parity-violating mixing matrix element between oppositeparity compound nuclear states from measuredasymmetries' and developed the theory relating thesematrix elements to the weak meson-nucleon couplingconstants. Using the above data we have determined avalue for the isoscalar p-nucleon weak coupling.

The 2 3 8U and 232Th data more than doubled thenumber of nuclear states for which parity-violatingasymmetries had been observed. Remarkably, all ten of

the statistically significant asymmetries had the samesign. This result was not expected on the basis of thestatistical theory of the compound nucleus, whichpredicted that the asymmetries would have random signs.Stimulated by these unexpected results, we and a numberc\ other authors have extended the theory of parity-violating asymmetries in the compound nucleus toaccount for a nonzero average parity-violatingasymmetry.4"7 This work and its interpretation hasfundamentally altered our understanding of the compound-nuclear-reaction mechanism. The parity-violatingasymmetries fluctuate around an average value. Thefluctuations are determined by the mixing of nearby s-wave resonances into each p-wave resonance. The mixingmatrix elements of the weak interaction have a statisticalcharacter. The average asymmetry results from themixing of levels several MeV away from each p-wavelevel. The mixing matrix elements of the weakinteraction have a single-particle character. The role ofdistant state and the relevance single-particle matrixelements in compound nuclear processes is an entirelynew development. The above explanation has a majorproblem. The above works are all flawed. The single-particle mechanism requires a weak-interaction strengthtwo orders of magnitude larger than that required toexplain the fluctuating component of the asymmetry, toaccount for the sizes of parity-violating observables inlight nuclei or the weak-interaction strength estimatedfrom meson-exchange models, h is clear that moresensitive and more extensive measurements of parity-violating asymmetries in the compound nucleus areneeded.


During the summer of 1992, we have completelyrebuilt our apparatus. We have purchased and takendelivery of a new cryogenic polarizing spin filter. Thisdevice will increase the beam polarization to a value of90% over a 8-cm-diameter beam spot. We are installing anew 1()B loaded liquid scintillator neutron detector, whichwill provide 90% neutron detection efficiency from 0 to10 keV. We are developing a capture y detector, whichwill allow us to study very weak p-wave resonances and touse separated isotope targets. In addition, we arerebuilding our collimators, monitor detector system, andspin transport system. These impartments will increasethe sensitivity of our measurements by a factor of 20.

We have begun preliminary studies leading to tests oftime-reversal symmetry in the compound nucleus. Wehave measured the depolarization of neutron spin as itpasses through a single crystal of ' ^ H o at 4 K. Asignificant degree of depolarization was observed for 0.7-eV neutrons. We are extending these measurements tohigher neutron energies. Our conclusion based on the 0.7-eV measurements is that depolarization can be understoodin terms of the domain structure of Ho. Depending on the

results of the depolarization measurements at higherenergies and on the parity-violation measurements, wewill begin the study of time reversal symmetry in 1993.

References

1. J. D. Bowman, C. D. Bowman, J. E. Bush, P. P. J.Delheij, C. M. Frankle, C. R. Gould et al.. Phys.Rev. Leu. 65. 1192 (1990).

2. C. M. Frankle, J. D. Bowman, J. E. Bush. P. P. J.Delheij, C. R. Gould, D. G. Haase et al.. Phys. Rev.Lea. 67, 564 (1991).

3. Mikkel B. Johnson, J. D. Bowman, and S. H. Yoo.Phys. Rev. Lett. 67, 310 (1991).

4. J. D. Bowman, G. T. Garvey, C. R. Gould, A. C.Hayes, and M. B. Johnson, Phys. Rev. Lett. 68, 780(1992).

5. S. E. Koonin, C. W. Johnson, and P. Vogel, Phys.Rev. Lett. 69, 1163 (1992).

6. V. V. Flambaum, Phys. Rev. C 45. 437 (1992).7. N. Auerbach, Phys. Rev. C 45, R514 (1992).


EXPERIMENT 899 - LEP

A measurement of the neutron deformation of 165Ho bypion single charge exchangeINSTITUTIONS: Los Alamos National Laboratory, Arizona State Univ., Stanford Univ., Univ. of Colorado, Franklin

and Marshall College

PARTICIPANTS: J. N. Knudson (spokesperson), J. D. Bowman (spokesperson), S. I. Penttila, J. R. Comfort(spokesperson), B. G. Ritchie, J. Gorgen, D. Mathis, J. Tinsley, S. S. Hanna, B. King, D. Pocanic,R. A. Loveman, L. S. Fritz, and N. S. Dixon

The collective behavior of nucleons and the shapes ofnuclei are among the most fundamental and intensivelystudied issues of nuclear physics.' Extensive informationexists in the literature concerning charge distributions innuclei: this information has come from a variety oftechniques, such as electron scattering, Coulombexcitation, and muon;c-x-ray experiment. Until now,however, there has been no direct experimentalinformation concerning neutron distributions in nuclei; asa result, equality between the charge (i.e., proton) andneutron distributions has been the most commonly madeassumption.

Nuclear shapes are typically described by a multipoleexpansion of the radii in terms of .spherical harmonicswith coefficients PL. The best systematic information onnuclear charge distributions comes from elastic electron-scattering experiments where hexadecapole parameters areroutinely determined. Hadron scattering similarly yieldsinformation on mass (neutron plus proton) distributions.However, due to many difficulties involved in theextraction of the matter deformation parameters, theresults of the hadronic experiments are not alwaysconsistent.

The motivation for this experiment was thesuggestion by Chiang and Johnson-1 that the orientationasymmetry,

As =- d o+ da 1/dQ

(1)

for the (Jt+,Jt'*) charge exchange reaction leading to theisobaric analog state is very sensitive to the ratio P2/P2 °fneutral and charge quadrupole deformations. In Eq. (1),

* 1/dQ; is the differential cross section for the

reaction with the symmetry axis of the deformed nucleusaligned perpendicular (parallel) to the direction of theincident beam. Chiang and Johnson further concluded4

that the deformation ratio should also not be verysensitive to uncertainties in the reaction model.

This experiment determined the orientationasymmetry for 165Ko, a highly deformed nucleus forwhich the charge distribution is well known. Single-crystal holmium is also known for its alignmentproperties; that is, at temperatures below 100 mK, thenuclear-spin axes of the holmium nuclei are almostcompletely aligned in the basal plane of the crystal lattice.We obtained single-crystal 165Ho target material thatpermitled placing the basal planes of the crystal structurein the plane perpendicular to the incoming pion beam inorder to obtain the da^/dD data. This arrangement,however, precluded the possibility of obtaining a parallelalignment; therefore, the asymmetry we report is

Ar =- do/dQ

+ do/dQ(2)

where do/d£2 is the differential cross section for adisordered target sample. Figure 1 shows Ar as a functionof the ratio P2/P2 'n l n e theory of Chiang and Johnson.

The holmium target was cooled in a 'He-^He dilutionrefrigerator placed in the LEP beam line. The dilutionrefrigerator maintained a target temperature of 70-80 mKwith the pion beam on target. The target sample wasresistively heated to >2 K to achieve the disorderedalignment state. Thermometry was accomplished with agermanium diode resistance thermometer. The targettemperature was the only experimental parameter allowedto vary, thus minimizing systematic errors.


Fig. 1. The functional relationship between thealignment asymmetry Ar and the quadrupole deformationparameter ratio ji'l / /J? for !f)5Ho single charge exchangeat )65 Me V.

The experiment-' was performed in the LEP beam linewith 165-MeV pions. The LAMPF jr° spectrometer6

was used to detect the neutral pions created in the reactionl65Ho(7t+.7i°)165Er. The spectrometer was set at 0°; thetotal angular acceptance was about 12°. The energyresolution for monoenergetic 7t°s was 2.6 MeV (FWHM).Cross-section normalizations were obtained using theintegrated LAMPF proton-beam current and the activationof scintillator disks.7 An ionization chamber was placeodownstream of the target cryostat to monitor fluctuationsin the relative beam fluxes, which allowed us to determinethe relative beam flux to <\%. Two complete warm-coldtemperature cycles were made.

The data were analyzed using methods developed byearlier users of the spectrometer. The solid angle of thespectrometer was determined by Monte Carlo simulation-**and the angle-sorted spectra were analyzed with a least-squares routine that simultaneously extracts areas underthe IAS peaks, the other resonances present, and thenonresonant background.y Figure 2 shows ihe forward-angle spectrum of each alignment state along with thecalculated fits. Figure 3 shows the extracted asymmetriesA r for the IAS transition as a function of the scatteringangle.

In order to extrapolate the asymmetry to 0°, the IAScross sections for each target-alignment slate were fit tothe function.

its)

rb. u

nn

(Ai

5

io

IC

ross

Af\f\

200

0

200

0

165Ho(7t+, 7t°)155Er

e = 3.5°Oriented Target

e = 3.5°Unoriented Target

100 120

7i° Kinetic

4

A

; M

140 160

Energy (MeV)

Fig. 2. Forward-angle K ® kinetic energy spectra for thealigned (upper) and the unaligned (lower) target stales.The smooth curves are the results of least-squares fits tothe isobaric analog stale, the other giant resonancespresent, and the nonresonant background.

010) = a{Jo(qR) + "(A6)2 (3)

as described in our earlier paper;7 the overall amplitude (a)and the effective scattering radius (R) are the only fittingparameters. This equation is simply an expression of theestablished1" Bessel-like behavior of single-charge-exchange scattering, with an additional term to account forthe finite spectrometer angular acceptance over a givenangle bin. We obtain a = 880 ± 30 and 920 ± 40(arbitrary units;, and R = 5.9 ± 0.2 and 5.4 ± 0.2 for thealigned and unaligned states, respectively. We deduce

A r(0') = -0.022 ± 0.024 . (4)

Equation (3) was used with these \alues of a and R toobtain the functional form of Ar shown in Fig. 3.

24

Research

0.4

0.2

-0.4

165Ho(7T, jto)'65Er(IAS)

T I = 165MeV

5 10

Scattering Angle, 6 (deg)15

Fig. .?. Extracted asymmetries Ar showing the angulardependence. The solid smooth curve is the functionalresult of fitting the cross-section data from each alignmentstate with Eq. (3). The dotted line is the result of thecoupled-channels calculation ofRef. 11.

A value of P^PS may be extracted from our value ofAr(0°) by use of the model relationship shown in Fig. 1.We obtain

= 0.84 + 0.08 . (5)

A calculation of Ar has also been made'' that employsHartree-Fock densities and a coupled-channels treatment ofthe reaction mechanism. While the difficulties of thiscalculation may limit its applicability to deducing p"/PHfrom Ar(0°), it does predict an angular distribution whoseshape, shown as the dotted line in Fig. 3, is not unlikethat displayed by the data. The magnitude of thiscalculation is a direct consequence of having the value(J7/P2 = 0.96 as an input parameter.


We conclude that the neutron distribution on 165Hois considerably less deformed than the charge (proton)distribution, significantly less so than can be computed bythe best-available Hartree-Fock models. Furthermore, theshape, but not the magnitude of the empirical angulardistribution of the alignment asymmetry, agrees with thatcomputed by the best available coupled-channels methods.These data pose new challenges to models of nuclearstructure and reaction mechanisms.

References

1. A. Bohr and B. Mottleson, Nuclear Structure(Benjamin, Reading, Massachusetts, 1975), Vol. II.

2. J. L. Friar and J. W. Negele, in Advances in NuclearPhysics, M. Baranger and E. Vogt, Eds. (PlenumPress, New York, 1975), Vol. 8, p. 219.

3. H-C. Chiang and M. B. Johnson, Phys. Rev. Lett.53, 1996 (1984).

4. H-C. Chiang and M. B. Johnson, Phys. Rev. C31,2140(1985).

5. J. N. Knudson, J. D. Bowman, S. I. Penttila, J. R.Comfort, B. G. Ritchie, J. Gorgen et al., Phys. Rev.Lett. 66, 1026 (1991).

6. H. W. Baer, R. D. Bolton, J. D. Bowman, M. D.Cooper, F. H. Cverna, R. H. Heffner et al., Nucl.lnstrum. Methods 180, 445 (1981).

7. J. N. Knudson, J. R. Comfort, R. A. Gianeili, B. G.Richie, D. Rothenberber, D. Pocanic et al., Phys.Rev. C35, 1385 (1987).

8. S. Gilad, Ph.D. thesis, Tel-Aviv University, 1979(unpublished).

9. A. Erell, J. Alster, J. Lichtenstadt, M. A. Moinester,J. D. Bowman, M. D. Cooper et al., Phys. Rev.C34, 1822 (1986).

10. M. B. Johnson, Phys. Rev. C 22, 192 (1980).11. J. Bartel, Mikkel B. Johnson, and M. K. Singham,

Ann. Phys. (N.Y.) 196, 89 (1989).



Search for the exotic decay |LI+ —» e+VgV^INSTITUTIONS: UC Irvine, Los Alamos National Laboratory, Univ. of Maryland, Argonne National Laboratory, Univ. of

Tel-Aviv (Israel)

PARTICIPANTS: R. C. Allen, H. H. Chen, R. Hausammann, W. P. Lee, X-Q. Lu, H. J. Mahler, K. C. Wang, T. J. Bowles,R. L. Burman (spokesperson), R. D. Carlini, D. R. F. Cochran, P. J. Doe, J. S. Frank, M. E. Potter, V. D.Sandberg, D. A. Krakauer, R. L. Talaga, and E. Piasetzky

Introduction

The conservation of lepton quantum number is one ofthe most extensively tested selection rules in particlephysics. There is no confirmed evidence for violation ofthe "additive law," where the sums of the individuallepton numbers Lf (f = e,|i,T) are separately conserved.However, the additive lepton conservation law is a purelyempirical rule; other "laws" have been suggested, such asa multiplicative lepton number conservation, where thetotal lepton number I ( L e + L u + LT) is constant, but theseparate numbers are each conserved according to theproduct I~l(-1 )L f . The gauge symmetries of the StandardModel do not require such laws. As a test of thisphenomenon, the Exp. 225 collaboration has searched forthe exotic muon-decay mode, \i+ —» e+VeV^. This decayoccurs in an attractive class of left-right symmetricmodels.'

The muon decay to the "wrong neutrinos,"

—> e + (I)

is an example of a process prohibited by the additive law,but allowed by the multiplicative law of lepton numberconservation. A previous direct search at LAMPF- fordecay (I) obtained a branching fraction limit R = r(ju+ —>e + v u v e ) / r ( ) i + —> all) < 0.09. Stronger evidence against amultiplicative law has been reported by the CHARMgroup, which searched for the inverse decay. v u + e~ —>\x~ + v e ; their result can be interpreted as R < 0.05.

Experiment

The experiment was performed at the LAMPF Line-Abeam stop, as part of the electron-neutrino electronscattering experiment.3 In the 800-MeV proton beamstop, n+ and | i + decays produced neutrinos with up to52.8-MeV kinetic energy. A total of 1.12 x 1023 protonswere incident at the beam stop during the experimentalexposure, resulting in 9.28 x 1021 muon decays at theneutrino source. The neutrino fluence at the detector,located 898 cm from the beam stop, was (9.16 ± 0.67) x1014 cm"2 for each of the three neutrinos produced in the7t+ —» |U+v —» e+v v cascade. The LAMPF beam energywas below kaon-production threshold, so 7i+ and JU+

decays were the only significant sources of beam-stopneutrinos. Nuclear absorption of negative pions andmuons reduced v e contamination from u.~ decays at rest toless than 5 x 10~4 of the n + decay flux.

The appearance of electron antineutrinos arising fromthe exotic decay mode, Eq. (1), would be signaled byinverse-beta decay of protons, v e + p —> e + + n, in ahydrogen-rich 3 x 3 x 3.5 m3 15-lon tracking calorimeter.The positron would trigger the detector, which consistedof repeated modules of helium-neon gas-filled Hashchambers for charged-particle tracking and plasticscintillators for triggering and energy measurement. Datareduction was designed to select single electrons producedin neutrino reactions, as identified by dE/dx. track, andevent isolation characteristics.

26


Results

The possible signal from exotic muon decay resultsin a more energetic positron spectrum compared toelectrons from the v e charged-current backgroundreactions, and from neutrino-electron scattering. This isbecause the p —> n transition has a low thresholdcompared to the background nuclear transitions (such asC —> N) and also because muon decay produces a moreenergetic antineutrino spectrum compared to the neutrinospectrum.

The measured angular and "visible energy" distribu-tions of the final event sample are shown in Fig. 1. The"visible energy" recorded in the scintillators is approxi-mately 60% of the total energy deposited in the detector.The light solid line in Fig. 1 represents the contributionexpected from exotic muon decay for the branchingfraction, R = 0.05, corresponding to the previous limitsagainst this mode. An experimental value for R isextracted from the data by determining the observedinverse-beta event rate from a muKiparameter fit to thecorrelated (0e, Ee) spectra, where the free parameters arethe normalization of the contributions from each of thevarious expected reactions. The fit result for inverse-betadecays, 148 ± 83 events, implies at a 90% confidencelevel that fewer than 256 vep events are observed.

The exotic muon decay branching ratio is calculatedby dividing the observed event rate of 148 ± 83 events bythe event rate of 14187 ± 1347 events obtained for R = 1,

R = RU.+ -+ all

1.48 ± 8 314187 ±T347

(90% C.L.). (2)

The upper limit4 for the exotic muon decay branchingfraction is R < 0.018 (90% C.L.). It should be noted thatneutrino oscillations through the v^ —> v e mode couldalso lead to the appearance of v e interactions, so that thelimit on inverse-beta events also implies limits onneutrino oscillations. At the two extremes of theoscillation parameter space, we find for large 8m*-,sin2(20) < 0.037, and for large mixing. 5m2 < 0.40 eV2.These results are consistent with previous limits, but donol exclude any new oscillation parameter space.

References

I. P. Herczeg and R. M. Mohapatra. "Muonium toAntimuonium Conversion and the Decay |a+ —>

150

S 100

(0

1"J 50

0

J

1\1

>

I

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10 20 30 40

Visible Energy (MeV)

50

IU

250

200

150

100

50

0

! I I- 0 » )

-

I I

I

JIT/

I

-

-

0.2 0.4 0.6 0.8

Cosine (%)1.0

Fig. I. Kinematic distributions of the final event sample.The heavy line is the result of the best fit obtained,assuming R = 0. The expected contribution from onlyve + p —> n + e+ for R = 0.05 is shown as the dashedhistogram, (a) Visible energy spectrum, (b) Cosine ofmeasured recoil angle.

e + v e v n in Left-Right Symmetric Models," LosAlamos National Laboratory document LA-UR-92-2089 (to be published in Physical Review Letters.1992); see P. Herczeg, in Rare Decay Symposium.Vancouver. Canada, D. Bryman et al. Eds. (WorldScientific, 1989), p. 24.

2. S. E. Willis, V. W. Hughes, P. Nemethy, R. L.Burman. D. R. F. Cochran et al.. Phys. Rev. Lett.44. 522 (1980): S. E. Willis. V. W. Hughes. P.Nemethy. R. L. Burman, D. R. F. Cochran et al..Phys. Rev. Lett. 45. 137()(E), (1980).

27


3. R. C. Allen, H. H. Chen, P. J. Doe, R. 4. D. A. Krakauer, R. L. Talaga, R. C. Allen, H. H.Hausammann, W. P. Lee et al., Phys. Rev. Lett. 64, Chen, P. J. Doe et al., Phys. Lett. B 263, 5341330(1990). (1991).

28



Experimental study of neutrino propertiesINSTITUTIONS: UC Irvine, Los Alamos National Laboratory, Univ. of Maryland, Argonne National Laboratory, Univ. of

Tel-Aviv (Israel)

PARTICIPANTS: R. C. Allen, H. H. Chen, R. Hausammann, W. P. Lee, X-Q. Lu, H. J. Mahler, K. C. Wang, T. J. Bowles,R. L. Burman (spokesperson), R. D. Carlini, D. R. F. Cochran, P. J. Doe, J. S. Frank, M. E. Potter, V. D.Sandberg, D. A. Krakauer, R. L. Talaga, and E. Piasetzky

Introduction

During the course of the Exp. 225 measurement1 ofelectron-neutrino-electron elastic scattering, ve + e~ ->ve + e~, we studied various properties of neutrinos:electromagnetic form factors, flavor-changing neutralcurrents, and lifetimes. The experiment utilized theintense flux of neutrinos at the LAMPF Area-A protonbeam stop. These neutrinos were produced from stopped7t+ decays, which made 29.8-MeV v u , followed bystopped \i+ decays, which made vu and ve with end-pointenergies of 52.8 MeV. For the beam exposure of 1.12 x1O^3 protons, the total resulting time-integrated neutrinofiux for each of the three neutrino types was 9.16 ±0.67 x 10'4 v/cm^, at the average detector distance fromthe beam stop of 898 cm. The Exp. 225 neutrino detectorconsisted of two basic components: a system of activeand passive shielding, used to reject incoming chargedparticles, surrounded by a 15-metric-ton central trackingdetector. This central detector was used to measure theenergy (resolution of 14%) and track direction (resolutionof 8°) of the recoil electrons. It was arranged in a verticalsandwich structure of forty identical layers and comprised4.94 x l(pO target electrons. For our energy threshold,the electron from ve~ scattering recoiled along theneutrino direction with an angle less than 16°. whereasbackgrounds from both cosmic rays and acceleratorneutrons were essentially isotropic. The ve~ signal isthen apparent in the recoil angular distribution as apronounced peak in the forward direction. The experi-mentally observed angular distribution, and clear ve~peak, is shown in Fig. 1. It is the comparison of themeasured ve~ strength to that predicted by the electroweakStandard Model that places limits on nonstandard physics.

Fig. I. The obsen>ed angular distribution of the beam-associated recoil electrons. Here, 6ev is the angle betweenthe incident neutrino and the reconstructed recoil electron.The solid line indicates the fit to the Monte Carlodistributions for the expected signal and backgrounds. Thedotted line indicates the total background, while the dashedline indicates the neutrino-induced background only.

A listing of neutrino properties, and of the new resultsreported here by the Exp. 225 collaboration, are displayedin Table I.

Electromagnetic Moments

A neutrino magnetic moment would be manifest asan excess of elastic-scattering events. A fil :o the

29


Table I. Properties of ve

Exp. 225 are given in the

Type

and v u Neutrinos,final column.

Property

The present values and limits are listed

Value

in the third column.

New

New limits from

Limit

Mass

Charge

Spin

Hv

| r I1-fee

9eV

0

1/2

<7x

>5 x 103 sec/eV

<12 x 10"1

<2.3 x 10"1 6 cm

<0.35

Mass

Charge

Spin

Irl1 - t'uu

T/mV M

270 keV

0

1/2

<8.5x

< l . 6 x 1 0 - 1 6 c

9

>0.11 sec/eV

8.1 x 10-1(VBohr

>!5sec/eV

experimental angular distribution is used to determine theelastic scattering signal, since the shape of the angulardistribution is approximately the same for both magneticand weak scattering, and yields 274 ± 37 observed elastic-scattering events. For the nonneutrino value of sin-9\v =0.227, the expected event rate is 285, including 224 vee~and 61 (vu + vu)e~ elastic-scattering events. Folding in asystematic uncertainty of 8.8%, we find -11 ± 35(stat) ±25(syst) events above expectations from the minimalStandard Model. Including systematic and statisticaluncertainties, the observed event rate due to magneticmoment scattering is N 0(,f < 68 events at 90%confidence level.

The number of events expected from magneticmoment scattering is (5.86 x IO19)f"v events fromelectron-neutrinos and, assuming equal magneticmoments, (1.23 x IO2(')fv events from inuon neutrinosand antineutrinos combined; here, fv is the neutrinomagnetic moment in Bohr magnetons. For the upperlimit of N ohs = 68. the experiment gives- 90%confidence limits on the neutrino magnetic moments ofHVV < 11.8 x i n - l « M B o h r and MVM < 8.1 x 10~' °MBohr- The upper limit obtained for HVc ' s consistent

with that for jave from a reactor experiment, while thebounds on (j.V(i are more restrictive than previous results.

In contrast with the magnetic dipole moment, theneutrino charge radius is not gauge invariant; nevertheless,a measurable neutrino charge-radius form factor can bedefined-' for low q2 laboratory interactions as an additivecorrection to the effective weak neutral-current vectorcoupling, gy- A nonzero charge radius shifts gv from itsuncorrected value of gv = -(1/2) + 2sin29\y to gy =-(1/2) + 2(sin20\v + 5 ) , where sin28\v is 'he weakmixing parameter measured in nonneutrino interactionsand 5 = (V2jia/3GF)<r2> = 2.39 x 10™ cirr2<r2>. Thevee~ signal, used to evaluate gy, is obtained from a two-dimensional fit to the recoil electron angle and energydistributions. This procedure yields 234 ± 35 v e e~elastic-scattering events remaining and gives the 90%confidence interval -0.214 < gv < 0.214.

From the W± and Z° masses, s i n 2 9 w = 0.227. andwith the measured confidence interval for gy ' r o n l ln>s

experiment, the radiative correction is -0.170 < 28 <0.260. This leads4 immediately to the 90'7r confidencelimits. -3.56 x H)"-12 cm2 < (r2) < 5.44 x H)'32 cm2.Thus, the v c charge radius is | r | < 2.2 x 10~1(i with

Research

90% confidence, which represents a new upper bound onthe dimensions of internal structure of the electronneutrino. This result can also be interpreted directly as anupper limit against a possible ve anapole moment.

Flavor-Changing Neutral Currents

Consideration of weak neutral currents has beencentral to the development of the Standard Model ofelectroweak interactions. Much of the formal structure ofthe Standard Model derives from the necessity to eliminateflavor-changing neutral currents (FCNC) at the tree-level,since such currents have not been observed experi-mentally. Because the vee~ scattering is mediated by theexchange of both W and Z bosons, the outgoing neutrinois required to be the same type, i.e., ve. as the incomingneutrino; thus vee~ is sensitive to FCNCs. A convenientway to search for such a phenomenon would be tocompare the measured value of the weak-mixing anglefrom v ee~ scattering. By/, with that extracted fromnonneutrino processes. A framework in which to discussFCNC in neutrino-lepton currents begins with theintroduction-^ of purely phenomenological couplings fee,fejj. and fet, where I = €e + *(fu. + fer a n d l n e StandardModel is recovered by setting feu = feT = 0.

If we label the weak-mixing angle extracted fromvee~ elastic scattering as 8\y. and the weak-mixing anglederived from the W^ and Z^ masses as 0\y. w e have

1 - fee = (sin20w - sin20\v) x

A

11 + ^(sin29w + sin26w)]( 1 - 2sin29w)"' •(I)

Explicit limits can be imposed by use of the range forgygiven above, the Standard Model relationship gv =-(1/2) + 2sin29\v- and the nonneutrino-derived valuesin29\v = 0.227 from the W* and Z° masses. A MonteCarlo calculation then yields the mean value fee = 0.93.and the 90% confidence limit for an off-diagonal, flavor-changing coupling, as I - fcc < 0.35. Alternatively,through use of the normalization relation, we have a limiton the total strength of flavor-changing transitions of1'eu + I'ei < (>-5


Muon-Neutrino Radiative Lifetime

It is not known if the neutrino is absolutely stable,and. if not. by what modes it would decay. Neutrino decayrequires lepton flavor violation and the existence of atleast one massive neutrino species. The electromagneticdecay, v —> y + X, is especially interesting because it canbe related to the internal structure of the neutrino. Wehave looked for this mode in an appearance experiment, bysearching within the 31.5-nv1 Exp. 225 tracking detectorfor the presence of gamma rays. The observed y-raysignal. Ny, is related to the radiative lifetime, T. through

d/c m v

t F:V 'NY=eI ( ) (2)

where e is the experimental detection efficiency for decayphotons, I() is the incident neutrino intensity, d/c is thetime the neutrino spends inside the sensitive volume, andEv /mv is the relativistic time-dilation factor. The bestprevious laboratory limit for the muon neutrino decay,6

x/mV(J > 0.11 sec/eV, was measured at the same site, withthe same neutrino source, in LAMPF Exp. 31.

Although the matrix element for neutrino decay isunknown, the angular distribution can be assumed to havethe general form dNy = (J/2)(l + a cosG)d(cos9) in theneutrino rest frame. The anisotropy parameter, a, is identi-cally zero for Majorana neutrinos, but can take on anyvalue -1 < a < I for Dirac neutrinos.

This experiment is sensitive to gamma rays in theenergy range 15 MeV < Ey < 53 MeV. Due to therelativistic focusing of the decay photons along theincident neutrino direction, electrons observed as a signalof radiative neutrino decay are kinematically constrained torecoil at small angles to the incident neutrino direction.This experiment was designed to detect forward-goingelectrons as a signal of ve~ elastic scattering. Thus, theobserved data sample contains contributions from bothelastic scattering and a possible neutrino-decay signal.For any single decay, two-body kinematics determine thelab-frame energy of the decay gamma ray. Ey. in terms ofthe lab-frame energy of the neutrino. Ev. and eenter-of-mass decay angle 9. Ey= Ev( I + cos9)/2. where the final-state particles are assumed massless. For this experiment.Ev » mv so that all rest-frame emission angles areLorentz contracted into an extremely narrow range alongthe neutrino direction in the laboratory frame. With all


emission angles contracted into the forward direction, themain observable consequence of the anisotropy is in thelaboratory-frame energy spectra of the decay photons. Theobservation from the measured angular distribution of274 ± 36 forward-angle electron events, in good agree-ment with the Standard Model prediction of 285 ± 26 suchevents, indicates that at 90% confidence level, there areNy < 68 events due to processes outside of standardelectroweak interactions.

The expression for the neutrino lifetime, obtained byrearranging the above equation, is T./mv =(Iod/Nyc)(e/{EV)), where the first factor is composed ofexperimental constants, and the second factor must becomputed for each neutrino flavor and anisotropy a.Given Io = 8.52 x 1019 v, d/c = 1.16 x 10~8 s, and Ny =68 events, the experimental constant is 1.45 x 1010 s; thesecond factor is determined with a Monte Carlocalculation. Under the assumption of equal radiativelifetime for vu and v^, limits obtained for each may becombined to yield'' T/mV)i > 15.4 sec/eV for a = - I ,increasing to t/mVti > 58.7 for a = 1.

References

1. R. C. Allen, H. H. Chen, P. J. Doe, R.Hausammann, W. P. Lee, H. J. Mahler et al., Phys.Rev. Lett. 64, 1330 (1990).

2. D. A. Krakauer, R. L. Talaga, R. C. Allen, H. H.Chen, R. Hausammann, W. P. Lee et al., Phys. Lett.B252, 177(1990).

3. G. DeGrassi, A. Sirlin, and W. J. Marciano, Phys.Rev. D39, 287 (1989).

4. R. C. Allen, H. H. Chen, P. J. Doe, R.Hausammann, W. P. Lee, X-Q. Lu et al., Phys. Rev.D43, Rl (1991).

5. L. B. Okun', Yad. Fiz. 41, 1272 (1985) [Sov. J.Nucl. Phys.4l, 812 (1985)].

6. J. S. Frank, R. L. Burman, D. R. F. Cochran, P.Nemethy, S. E. Willis, V. W. Hughes et al., Phys.Rev. D24, 2001 (1981).

7. D. A. Krakauer, R. L. Talaga, R. C. Allen, H. H.Chen, R. Hausammann, W. A. Johnson et al., Phys.Rev. D44, R6 (1991).

32



Search for neutrino oscillations with high sensitivity inthe appearance channels v^ —> ve and Vjn —> ve

INSTITUTIONS: UC Irvine, UC Riverside, UC Santa Barbara, UC IIRPA, Embry Riddle Aeronautical Univ., LinfieldCollege, Los Alamos National Laboratory, Louisiana State Univ., Univ. of New Mexico, Univ. ofPennsylvania, Southern Univ., Temple Univ., Valparaiso Univ.

PARTICIPANTS: G. Yodh, J. H. Kang, W. Strossman, G. J. VanDalen, D. Bauer, D. Borden, D. Caldwell, A. Lu, S. Yellin,D. Smith, A. Eisner, M. Sullivan, W. Vernon, Y. Wang, I. Cohen, D. Schnitzler, R. D. Bolton, R. Burman,J. Donahue, F. Federspiel, W. Foreman, G. T. Garvey, T. Kozlowski, W. C. Louis (spokesperson), J.Margulies, V. Sandberg, M. Schillaci, D. H. White, D. White-house, R. Imlay, C. Lyndon, W. Metcalf, G.Singha, B. B. Dieterle, C. P. Leavitt, R. Reeder, F. Schaefer, M. Albert, A. K. Mann, A. Fazely, C.Athanassopoulos, L. B. Auerbach, P. Hermida, V. Highland, D. Works, Y. Xiao, D. D. Koetke, and R.Manweiler

The Liquid Scintillator Neutrino Detector (LSND) hasbeen designed to search concurrently for v^ —> v e andVji —> v e oscillations with high sensitivity at LAMPF.The observation of neutrino oscillations would have aprofound impact on nuclear, particle, and astrophysics, asit would imply that lepton number is not conserved and

that neutrinos have mass and contribute substantially tothe mass of the universe.

The detector, shown in Fig. 1, consists of a tank with200 tons of dilute liquid scintillator with 1224 8" photo-multiplier tubes mounted on the inside tank covering 25%of the surface. Both Cerenkov light and scintillation light

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-AccessDoor

-Pb Shielding5.72 m 8.75 m

Experiment Tank8" Hammamatsu photomultipliers 44 tubes/rib21 ribs 150 tubes/each endcapRib spacing: 14.3"

Fig. I. A layout of the detector, which consists of a tank with 200 tons of dilute liquid scintillator and with 1224 8"photomultiplier tubes mounted on the inside surface.


will be detected. The tank will reside inside the existingExp. 645 veto shield, and the experiment wili make use ofthe present A6 beam-stop neutrino source to begin with.An A6 upgrade has been proposed, which would increasethe decay-in-flight neutrino flux by a factor of five, andwhich would greatly improve both the measurement ofneutrino-proton elastic scattering, which would determinethe strange quark contribution to the proton spin and asearch for muon-neutrino disappearance. After two yearsof data collection. 90% confidence level limits onVjjtv^) —> ve<ve) mixing strengths of 2.7(2.7) x l()~4

can be obtained for ail Am- > 1 eV-. Similarly, formaximal mixing, the 90% C.L. limits on Am 2 are1.7(4.0) x 10"-. This experiment will, therefore, providethe world's best terrestrial limits on vu —> ve oscillations.Other physics to be obtained include measurements of thecharged-current reactions veC —> e~N and v^C —> |i"N. ofthe inelastic neutral current reaction vC —> vC* (15.11-MeV y). and a search for the rare decays 7r() —> vv andr\ —> v v .

A significant amount of progress has been made inthe past year. The electronics caboose has beenconstructed and the racks and flooring installed. Also, therefurbishing of the Exp. 645 veto shield has begun. All ofthe phototubes have been removed, the removable flangesshipped to LSU for reworkirg. and the cleaning of thefixed flanges has started. The detector tank is fullydesigned and will be constructed in the spring. The tankwill contain 1224 8" Hammarnatsu phototubes, corre-sponding to a 25% photocathode coverage. The first 48phototubes have arrived and have been tested in thephototube testing laboratory, which has an 8-phototube-per-day capability.

A series of liquid scintillator tests was performed inthe LAMPF test beam during the summer in order todetermine an appropriate liquid .scintillator mixture. A2-m-long. 2"-diameter PVC pipe with a phototube at oneend was filled with liquid and placed in a beam line definedby four scintillator paddles. Figure 2 shows the measuredlight output from the pipe as a function of its anglerelative to the positron beam, for liquid mixtures of puremineral oil (circles) and mineral oil with 0.03 g/i ofb-PBD (crosses). Both liquids show prominent Cerenkovpeaks at an angle of 47°. while the b-PBD mixture alsoshows a Hat component of scintillation light. The b-PBDmixture emits scintillation and Cerenkov light in the ratioof approximately four to one and has the advantage oflosing very little Cerenkov light (<!()%) to scintillatorabsorption due to the short wavelength of the b-PBDabsorption spectrum. Also, the scintillator mixture

exhibits pulse-shape discrimination, which offers anotherway of separating protons from electrons, in addition tofitting to the Cerenkov cone. Finally, the attenuationlength of the liquid has been measured to be very long(>2() m) at moderate wavelengths (>42() nm).

The front-end electronics is almost fully designed, andprototypes of the front-end QT channels have been testedand shown to have excellent charge and time resolution.The data acquisition system will be based on SCSI andVME bus and will transfer data from the front-end cratesto a FARM of UNIX processors, which will fullyreconstruct events, and then to a Host computer, whichwill write the reconstructed data to storage. UNIXworkstations have been obtained for testing the datatransfer rate and the event reconstruction time. With the

/•/,(•. 2. The measured light output from the pipe us afunction of its angle relative to the positron beam, forliquid mixtures of pure mineral oil (circles) and mineraloil with 0.03 t>// ofh-FBI) (crosses).

Research

present reconstruction algorithm, the workstationsreconstruct a typical event in one second or less(depending on energy), which implies that a FARM offive or six processors will be sufficient for performing theexperiment.

The Monte Carlo simulation has been rewritten withthe GEANT software package. GEANT allows the simula-tion of not only the propagation of electrons and photonsthrough liquid scintillator, but also the propagation ofother particles such as protons, muons, pions, andneutrons. GEANT is also very convenient for fully


describing the detector geometry, including the photo-tubes, phototube mounting, and tank walls.

The collaboration expects to almost complete theLSND construction over the next year. The detector tankwill be constructed in the spring and the mixing tender andstorage tank by the end of the summer. The veto shieldrefurbishing will also be finished in the summer, as willthe testing of all 1224 8" Hammamatsu phototubes. Onceall of the phototubes have been mounted, the tank will besealed and filled with liquid scintillator in lime forengineering tests by the end of the year.



Measurement of the spin-longitudinal and spin-transversenuclear responses in the 12C(p,n) and 40Ca(p,n) reactionsat 495 MeVINSTITUTIONS: Los Alamos National Laboratory, Univ. of Colorado, Ohio State Univ., Indiana Univ., UCLA, Ohio Univ.

PARTICIPANTS: R. C. Byrd, J. B. McClelland (spokesperson), L. J. Rybarcyk, T. N. Taddeucci (spokesperson), T. A.Carey (spokesperson), X. Y. Chen, D. Mercer, D. Prout, S. deLucia, B. Luther, D. G. Marchlenski, E. R.Sugarbaker, C. D. Goodman, E. Giilmez, and J. Rapaport

The spin response probed by quasi-free (p,n) reactionsis of particular interest because of its relationship to thestrength and momentum-transfer dependence of the residualisovector particle-hole interaction. Collectivity inducedby this interaction is expected to produce significantdifferences between the isovector spin-longitudinal( a • q ) and spin-transverse ( o x q ) responses at amomentum transfer of about 1.75 fm~' (Ref. 1). Inprinciple, the two responses can be experimentallydistinguished by measuring complete sets of polarizationtransfer (FT) observables.-

The first measurement of the collective spin responseinduced by proton scattering involved (p,p') quasi-freescattering at 500 MeV and I8.5°.2 This measurementfound no evidence for the expected enhancement of thelongitudinal spin response with respect to the transversespin response. However, a lingering source of uncertaintyin interpreting the data is the mixed isoscalar and isovectornature of the (p,p') reaction. Ideally, this uncertainty isremoved by repeating the experiment using the pureisovector (p.n) reaction. This has now been done inLAMPFExp. 881.

Experiment 881 measured a complete set ofpolarization transfer observables for quasi-free scatteringon 2H. / 2 C . and 4 0Ca. The data were obtained at theNeulron-Time-of-Flight (NTOF) facility with a beamenergy of 495 MeV and a scattering angle of IS0.-' Theseconditions very nearly replicate those of the original (p,p')experiment. The data were obtained during run cycle 57 in1990. Replay and analysis proceeded through mid-1991and involved 271 nine-track 6250-bpi tapes. An additional

60 tapes of calibration data were written as part of Exp.1062, described elsewhere in this report.

The targets used consisted of CD2. natural carbon,and natural calcium. The carbon and calcium targets had athickness of 1 g/cra ' and the CD2 target was780 mg/cm . Observables for -H(p,n) were obtainedfrom the CD2 spectra by subtracting the carboncontribution. A sample subtraction is presented in thereport for Exp. 1062.

The data were obtained on a flight path of 200 in.The beam intensity and polarization averaged 80 nA and55%. Typical event rates were about 0.8 kHz (average)with a corresponding system live time of about 40%. Thepolarimetry efficiency of the NTOF detector system isabout 0.75%. Approximately one day of beam on targetwas required for each incident polarization stale per target.

Two different neutron precession schemes are requiredto measure polarization transfer obscrvables at nonzeroangles. The magnets involved are shown in a layout ofthe NTOF swinger cave in Fig. 1. For sideways (S) andlongitudinally (L) polarized beams, the vertical dipole fieldof the sweep magnet (NTBM06) is used to precess theoutgoing L component into N (normal to reaction plane)polarization at the detector. The outgoing S polarizationis unaffected by this field, while the induced N-typepolarization is precessed into L polarization at thedetector. Because the induced N-lype polarization is nowunobservablc, reversal of the proton polarization alsoreverses the observable components of neutronpolarization incident on the detector. This reversal allowscancellation of instrumental asymmetries. For

36


NTOF Cave

Fig. 1. Schematic layout of the NTOF beam-swinger cave. The dipole magnets BM5 and BM6 are the dump and sweepmagnets and are also used to precess neutron polarization at 0°. For the IH° measurements described in this report. BM5 ismoved out of the neutron path and BM6 and NTSO (solenoid) are used to precess the neutron polarization.

measurements with N-type beam, the field in NTBM06 isreduced for minimum precession effect (it cannot be turnedoff because this magnet must still function as a sweepmagnet) and a superconducting solenoid (NTSO) at theexit aperture of the neutron collimator is used to precessthe outgoing N type polarization alternately by ±90°.These reversals are again necessary for cancellation ofinstrumental asymmetries.

The N-N scattering matrix is a useful starting pointfor discussion of the results. A common form is

M = A + C(O|n + (J2n) + BG|nG2n

+ EoiuO2a + FO|na2n • 0)

where the coordinates q = kj- - kj. n = kj x kf. and p = q xn are defined in terms of the initial and final c m .momenta k j and k j-. The coefficients in Eq. (I) can besubdivided into isoscalar (AT = 0) and isoveclor (AT = 1)components. In the following discussion, isovectoramplitudes are assumed.

In terms of the diagonal polarization transfercoefficients DJSJN. DS.S- un<J D u . in the laboratory


reference frame, longitudinal (q) and transverse (p) spin-flip probabilities can be defined for free scattering

and

Sq =

Sp =

- D N N + (DSs - DLL)sec(6|ab)] (2)

- D N N - (DSs - DLL)sec(8iab)]. (3)

spin-flip probabilities is proportional to the ratio ofeffective N-N amplitudes times the ratio of longitudinaland transverse spin responses Rq/Rp.

If the ratio of effective amplitudes is the same as theratio of free amplitudes, then the ratio of the two spin-flipprobability ratios

(Sq/Sp)A/(Sq/Sp)D = Rq/Rp (5)

The ratio of these two quantities gives the ratio of thelongitudinal and transverse N-N amplitudes [Eq. (1)],

Sq/Sp = E2 /F2 . (4)

For the present experiment, the quasi-free 2H(p,n) data areused to represent the "free" scattering observables. Thisshould be a very good approximation.

Similar quantities can be defined for scattering from anucleus, although the transformation from lab frame toc m . frame involves slightly more complicatedexpressions. For a nuclear target, the ratio of these two

yields the ratio of nuclear spin responses. Here "A" refersto the quasi-free ratio for nuclide A and "D" refers to thedeuterium ratio.

The essential point of this exercise is to emphasizedifferences between the free spin observables and the quasi-free spin observables. These differences contain the signalfor collectivity in the nuclear response or mediummodifications of the interaction. If the longitudinalresponse is collectively enhanced relative to the transverseresponse, the ratio in Eq. (5) should be larger than unity.

Figure 2 shows a comparison of the diagonal spinobservables for 2H, 1 2C, and 4(^Ca. It is clear from this

Fig. 2. Diagonal polarization transfer coefficients for (p,n) reactions on 2H, I2C, and 4(>Ca at 495 MeV and 1H°. Thevertical dashed line represents the energy loss for free N-N scattering. The solid horizontal lines represent phase-shift valuesfor the free observables.

38

figure that there is little difference between the quasi-freepolarization transfer for ' 2C and 4"Ca and that for freescattering, as represented by the 2H(p,n) data.

The ratio of spin-flip probability ratios is plotted inFig. 3. The (p,n) results obtained here are very similar tothe earlier (p,p') results. The ratio is everywhereconsistent with unity or somewhat smaller. The expectedlongitudinal enhancement is not seen. The results for'-C and ^°Ca are very similar and suggest that choice oftarget nuclide is not very important. This similarity isnot too surprising in view of the surface-peaked nature ofthe reaction.-

Several effects may conspire to suppress the expectedlongitudinal/transverse enhancement as seen in theexperimental ratio. In the surface region, decreased nuclear

a.

C/f

2

1.5

0.5

00

1 i c i ' i • i

-

d] 1

i > i

1 i ' i • I ' i •

• 12C(p,n) "D40Ca(p,n) .

_

P i i § § -i :

i , i , i , i ,

0 20 40 60 80 100 120 140 160 180

co (MeV)

Fig. 3. Ratio of spin-flip probability ratios. Thisquantity is proportional to the ratio of longitudinal andtransverse spin responses. The value of unity or smallerindicates no enhancement of the longitudinal responserelative to the transverse response.


density and mixing between the longitudinal andtransverse modes will both diminish the expectedsignature. Distortion effects must also be considered.What is needed is a calculation that combines both nuclearstructure and reaction dynamics in a realistic way.Ichimura et al. have performed distorted-waves RPAcalculations in a study of the (p.p') data, and are currentlyproducing new calculations for the (p,n) case. Thepreliminary conclusion to be drawn from the newcalculations is that the theoretical ratio is still too large inthe low-u) region, and best consistency with the data isobtained when the RPA correlations are turned off. Thisis a surprising result, and may indicate a problem with theassumed form of the residual particle-hole interaction.Additional experimental data at different momentumtransfers will help to understand this problem. Suchmeasurements are already planned for 1993.

References

1. W. M. Alberico, A. De Pace, M. Ericson, Mikkel B.Johnson, and A. Molinari, Phys. Rev. C38, 109(1988).

2. T. A. Carey, K. W. Jones, J. B. McClelland, J. M.Moss, L. B. Rees, N. Tanaka, and A. D. Bacher,Phys. Rev. Lett. 53. 144 (1984); L. B. Rees, J. M.Moss, T. A. Carey, K. W. Jones, J. B. McClelland,N. Tanaka, A. D. Bacher, and H. Esbensen. Phys.Rev. C34. 627 (1986).

3. J. B. McClelland, T. N. Taddeucci, X. Y. Chen,W. P. Alford, R. C. Byrd, T. A. Carey et al., Phys.Rev. Lett. 69, 582 (1992).

4. M. Ichimura, K. Kawahigashi, T. S. Jorgensen, andC. Gaarde, Phys. Rev. C 39, 1446 (1989).

5. M. Ichimura and K. Kawahigashi. "Extraction ofNuclear Spin Response Functions from SpinObservables of Nucleon Quasi-free Scatterings"(submitted to Physical Review C. 1992).

.VJ



Calibration of the NTOF detector system for polarimetryINSTITUTIONS: Los Alamos National Laboratory, Ohio State Univ., Univ. of Western Ontario (Canada), Univ. of

Colorado, Indiana Univ., UCLA, Ohio Univ.

PARTICIPANTS: T. N. Taddeucci (spokesperson), E. Sugarbaker (spokesperson), W. P. Alford, R. C. Byrd, J. B.McClelland, L. J. Rybarcyk, X. Y. Chen, D. Mercer, D. Prout, S. deLucia, B. Luther, D. G. Marchlenski,C. D. Goodman, E. Giilmez, C. A. Whitten, Jr., and J. Rapaport

The detector system used at the Neutron Time-of-Flight (NTOF) facility was designed specifically forneutron polarimetry with good neutron energy resolution.Jt employs a mineral-oil based liquid scintillator(BCol7s) that was formulated to have a moderately highhydrogen-to-carbon ratio (H:C = 1.7) along with goodlight output and timing characteristics.

The detector is shown schematically in Fig. I. Itconsists of four scintillator planes separated into two

CAO ceo

L, •NAO NA1

NCO NC1

ALXZ.

Fig. I• Schematic side view of the NTOF detectorsxslem. The two [rant detector planes I NAO. NAI) andthe first plane (NCO) in the hack pair are opticallysubdivided stainless steel tanks filled with BC-5I7s liquidscintillator. '/'lie fourth plane (NCI) consists often barsof plastic (HC-40H) scintillalor. Thin scinlillators (CAO.CCO) in front of each pair oj planes are used to lagcharged particles for trigger definition and event sorting.The average separation between the front and back pairs ofplanes is lypicallx 140 cm.

groups. Each plane is optically subdivided intoindependent cells approximately I m x JO cm x 10 cm insize. The front pair of scintillator planes analyzes thepolarization of incident neutrons via the reactions

*H(n,n) 'H and 'H(n,p)n and analogous quasi-freereactions on carbon. The back pair of planes delects thescattered neutron or reaction proton. Time and positioninformation from the interactions in the front and backplanes allows the velocity and angle of the secondaryparticle (neutron or proton) to be determined and comparedto the velocity of the incident particle. This eventreconstruction enables efficient rejection of frame-overlapneutrons, gammas, and cosmic rays. However, theinterplane time and position resolution are not sufficientto separate the free n + p and quasi-free n + C reactions.Thus, while the free n + p analyzing power is fairly wellestablished and could therefore be used to accurately modelthe polarimeter effective analyzing power, the unresolvedquasi-free component necessitates an empirical calibration.

During Cycles 56-58 in the summer of 1990, and althe end of Cycle 60 in 1991. measurements were madethat provide a calibration of the effective analyzing powerof the detector for neutron polarimetry over the energyrange from 31K MeV to 492 MeV. Three differentcalibration reactions were used.

The preferred calibration reaction is the '"*C(p.n)'"^N(2.31-MeV) reaction. This 0+ —> 0+ isobaric-analog-slate(IAS) reaction produces neutrons at a scattering angle of0 ' that have the same polarization as the incident protonbeam (D|,i, = DJJS = '^NN = ' )• The major source ofsystematic error in this type of measurement is theuncertainty in the proton beam polarization. Thedisadvantages of this reaction are the obvious hazardsinvolved with using a target that is intrinsically

40

Research

radioactive, the low count rates associated with a smallcross section, and the thin target and long flight pathrequired to achieve the energy resolution necessary toseparate the IAS transition from the strong Gamow-Tellertransition to the nearby 3.95-MeV state in '"*N.

A second calibration reaction that has advantages interms of both count rate and resolution is the -H(p,n)-preaction at zero degrees. For low energy loss, the tworesidual protons are restricted to be in a relative 'So state.The reaction therefore proceeds like l+—> 0+ . Thelongitudinal polarization transfer coefficient DLL(O°) forthis reaction was recently measured by McNaughton et al.for energies of 314, 494. 645. 731. and 797 MeV.' Themeasurements were made in a way that eliminates manypotential sources of systematic error. An additionaladvantage of this reaction is that simple CDT targets canbe used.

A third source of polarized neutrons is the quasi-free-H(p.n) reaction. At sufficiently large scattering anglesthe quasi-free neutrons can be separated from neutronscorresponding to the 2p final state. These neutrons willhave polarization observables similar to free n + pscattering. The symmetry relation P = A can be appliedto these neutrons to obtain the magnitude of the outgoingN-type polarization in terms of the easily measuredanalyzing power.

The '"*C(p,n) IAS reaction was used at an incidentenergy of Ep = 495 MeV to obtain a calibration point at aneutron energy of 492 MeV. A longitudinally polarizedproton beam (pi = 0.56) was used to producelongitudinally polarized neutrons via the polarizationtransfer DyjO0) = I. The outgoing L-type neutrons werefirst precessed by 45C in the horizontal plane by theNTOF dump magnet (NTBM05). The remaining Lcomponent was then precessed vertically by 90° in theNTOF sweep magnet (NTBM06). Approximately equal Inl-and S-type neutrons were therefore incident on thedetector. The detector was stationed at a flight path of400 m. The resolution obtained was approximately0.75 MeV averaged over all runs, with the best datahas ing a resolution of better than 600 keV. A spectrumrepresenting all final data is shown in Fig. 2.

A calibration based upon the P = A relationship forquasi-free -H(p.n) scattering was obtained by measuringN-type polarization for this reaction al Kp = 495 MeV and0 = IN . Al this energy and angle, the mean energy lossof the quasi-free neutrons is approximately 58 MeV. Thetarget used was C'DT. A separate measurement on a purecarbon target was used to subtract the carbon contributionfrom the C'DT. The measurements were made as part of


Exp. 881. A spectrum showing the quasi-free -H(p.n)cross section and analyzing power is presented in Fig. 3.

Measurements of DLL r o r t n e ~H(p.n)2p reaction at0° were made for Ep = 495 MeV and 318 MeV. The lattermeasurements were made during a short two-shift run inAugust 1991. This was the only beam time allowed toNTOF during 1991 because of radiation safety concerns.The higher energy measurements were made as part ofExp. 1062 and Exp. 881.

The results at 495 MeV. which are normalized to the1 4 C calibration, agree well with the independentmeasurements made by McNaughton et al. at very nearlythis same energy. This agreement suggests that thisreaction should be suitable for additional calibrationsabove 500 MeV. where the resolution requirements of the'"*C calibration pose great difficulty. The measurementsmade by McNaughton et al. have an energy resolutionmuch poorer (about 30 MeV al 500 MeV) than Ihalobtained in the NTOF measurements (I MeV). Thecorrections necessary to account for this resolution

1.2

—. 1 0

"5T£ 0.8a£ 0.6

i °4

> 0.2

0.0

0.0

-0.2

rf -0.4

-0.6

-0.8

-1.0

14C(p,n)9 = 0°

J».^P^-*< v •^•»"*y>

480 485 490Neutron Energy En (MeV)

495

/•'is;. 2. '/.ero-ilegree sped nun for '"'Clp.ii) al Ep = 4V5

MeV. The (>+ IAS transition is used to calibrate the

polarinwtcr analyzing power. I he htitwin half of the

lifiiire reveals the different polarization transfer character of

the stroiii; (VI slate.

4 I


^ 0.5

•jj 0.4

* 0.3

-§- 0.2

0.13©B" o.o

2H (p,n)495 MeV

0.4

0.3

0.2

0.1

on

'.~-

'-

i

59

_ T

* 1

• p• A :

T it 1

50 100 150(o (MeV)

Fin. 3. Spectrum for -H(p.n) at Ep = 495 MeV and 6 -18°. The quasi-free distribution peaks at an energy li>ss ofabout 60 MeV. The clotted vertical line marks the energytoss for free n + p scattering. A vestige of the 2p final-state interaction can be seen at an energy loss of about35 MeV.

mismatch are expected to be small, but are still beinginvestigated. A spectrum for CDitp.n) at 0° i.s shown inFig. 4.

Results of the calibrations are shown in Fig. 5. Alsoshown are the results of Monte Carlo simulations of thedetector using free n + p observables. The calculatedeffective analyzing powers agree quite well with theobserved values in the (n.p) channel. The quasi-free n + Ccontribution in this channel is therefore nol detrimental.This result is not surprising. Previous measurements ofthe analyzing power for '-C(p.n) quasi-free scattering at495 MeV revealed that the analyzing power for charge-exchange quasi-free scattering is very similar to freescattering. The situation is much different in the (n,n)channel, however. In this channel the effective analyzingpower is only 2/3 of the value based on free scattering.Again, this is not surprising. It is well known that theanalyzing power for quasi-free (p.p') scattering isconsiderably diluted with respect to the free value. In

ativ

e)(r

elel

d

>

a

1.0

0.8

0.6

0.4

0.2

0.0

0.0

-0.2

-0.4

-0.6

-0.8

-1.0

-

r

'-

470

, , . | , , i , | ,

CD2(p,n)W = 0Ep = 495 MeV

' " 1

'..,1, , 1 . , , , 1

475 480

Neutron

, i i | i .

p

, 1 , 1 , 1

485

Energy

i i i i i i i i i i i i j

n :

r \ '-s 1

, i . , .In , , . , :

;

. . f :i , , , , 1 1 , , , -

490 495 500

En (MeV)

Fig. 4. Zero-degree spectrum for CDifp.n) at Ep =495 MeV.

Neutron Energy En (MeV)

Fig. 5. Effective analyzing power for the NTOF detectoras a function of neutron energy. The solid lines representMonte Carlo calculations based on free n + p cross sectionand analyzing power. The dashed line is the (n.n)calculation normalized bx 2/3.

Research

relativistic reaction models, this difference has beenattributed to a sensitive cancellation of the scalar andvector potentials.- The same dilution should apply to(n.n) scattering, and a substantial quasi-free contributionfrom n + C will therefore have the observed effect uponthe polarimeter analyzing power.

Future calibration efforts will concentrate on650 MeV and 800 MeV. These calibrations are likely tobe done by normalizing to the -H(p,n) DLL measurementsof McNaughton et al., provided that the necessarycoiTections can be thoroughly understood.


References

1. M. W. McNaughton. K. Koch. I. Supek, N. TanakaD. A. Ambrose, P. Coffey el al.. Rhys. Rev. C 45,2564 (1992).

2. C. J. Horowitz and D. P. Murdock. Phxs. Rev.C 37, 2032 (1988).


EXPERIMENTS 876, 1072, AND 1234 - OPPIS

Nucleon-nucleon experiments using the Line B facilityINSTITUTIONS: Univ. of Texas at Austin, Los Alc.nos National Laboratory, Texas A&M Univ., Univ. of Colorado, Rice

Univ., Argonne National Laboratory, Univ. of Montana, Washington State Univ., Univ. of CentralArkansas

PARTICIPANTS: K. H. McNaughton, D. A. Ambrose, P. Coffey, K. Johnston, P. J. Riley, M. W. McNaughton(spokesperson), I. Supek, G. Glass, J. C. Hiebert, L. C. Northcliff, A. J. Simon, D. J. Mercer, D. L.Adams, H. Spinka, R. H. Jeppesen, G. £. Tripard, and H. Woolverton

The high intensity of the OPPIS optically pumpedpolarized ion source has made it possible to measure thespin-transfer parameters in np elastic scattering (Fig. 1).These ne* data, when combined with previous data,overdetermine the five complex amplitudes for both

isospin-0 and isospin-l NN scattering near 500, 650, and800 MeV. The np spin-dependent data set now includesthe analyzing power,'-- the four spin-correlationparameters,•'•5 and four spin-transfer parameters (Ref. 6and Fig. 1).

Fig. 1. Spin transfer parameiers for np scattering at 635 MeV compared with phase-shift fits b\ Bugg and A null.

44

Research

The new data have made a major impact on the phase-shift analyses.7"11 In 1991 Bugg and Bryan1" wrote,"There are not enough accurate spin dependent data to givea secure solution and most of the phase shifts are stronglycorrelated, with correlation coefficients as high as 76%."They now report "a colossal improvement" withcorrelations small and all phase shifts following smoothcurves up to 800 MeV.

Nevertheless, significant differences persist among thephase-shift analyses. There are active phase-shift analysisgroups in Virginia,7 France and Switzerland,^ Englandand Texas,9-'O and Japan,1 ' ' ' 2 and not all of these havefully digested the new data. With an over-determined database available for the first time, work has begun toidentify systematic errors in previous data and to cull thesefrom the data base.


Further differences among the different analyses arecaused by different assignment of the inelasticity amongthe available channels. The inelasticities are poorlydetermined by elastic measurements, and isospin-zeroinelastic data are almost nonexistent. A major programhas begun at LAMPF to accumulate sufficient data for apartial wave analysis of the NN inelastic reactions. ' 3 ' 1 4

Absolute calibration standards are an important spin-off from the NN program. The pp analyzing power15

(measured to better than 1%) and the pC inclusiveanalyzing power (2%)'^ are used worldwide as polarimetrystandards. Preliminary data (<1%) from the recentmeasurement of pp absolute cross sections17 are shown inFig. 2. The development of techniques to count theproton beam at rates up to 300 MHz (Ref. 18) led to a

Fig. 2. Ratio of the pp elastic cross section at 792 MeV to the phase-shift Jit by Bugg.


remeasurement of pd scattering,'9 resolving a long-standing discrepancy.

Recent measurements2" of the zero-degree D(p,n)spin-transfer to calibrate the neutron beam polarization areshown in Fig. 3. These new data disagree with olderdata,21 and resolve long-standing discrepancies with thesum rules22 and other consistency checks.-" Thesemeasurements provide a convenient calibration standard,with a large cross section, small background, and requiringlow resolution. This standard has been used to calibratethe long flight path neutron facility, NTOF, at LAMPF.

The mixing parameter epsilon-1 contains suchimportant physics (determining the tensor force, for

example) that it demands special attention. According tothe present analyses, epsilon-1 is about 9° near 800 MeVand may increase at higher energies, to the surprise ofmany theorists. The determination of epsilon-1 will bemuch improved by data for the normal-to-normal spintransfer KNN. which will be measured in 1992.

Measurements of the np analyzing power in 1992will clarify the remaining details of the neutron beampolarization, allowing us to renormalize the previous npdata that used the LAMPF BR polarized neutronfacility.1"5'23

-0.4

s£ -0.5

-0.6

-0.7

-0 8

i i i i i i i i i i i i i i i i i i i i i i i i _

s. ^ -- i— ^ w * * * * * * —

= , , , , i , , , , i , , =

300 400 500 600 700 800

Energy (MeV)

Fig. 3. Spin transfer parameter for D(p,n) at zero degrees compared with calculations by Bugg (solid curve) and thenpfree spin transfer (dashed).

References

1. C. R. Newsom, C. L. Hollas, R. D. Ransome, P. J.Riley, B. E. Bonner, J. G. J. Boissevain et al., Phys.Rev. C39, 965 (1989).

2. G. Glass, T. S. Bhatia, J. C. Hiebert, R. A.Kenefick, S. Nath, L. C. Northcliffe et al., Phys.Rev. C41, 2732(1990).

3. R. Garnett, M. Rawool, V. Carlson, D. Hill, K. F.Johnson, D. Lopiano et al., Phys. Rev. D40, 1708(1989).

4. M. W. Rawool, "The Measurement of the SpinCorrelation Parameters CSL and CLL in n p -» npScattering at Energies 484, 634, and 788 MeV,"Ph.D. thesis, Los Alamos National Laboratory reportLA-11387-T(1988).

46


5. S. Nath, G. Glass, J. C. Hiebert, J. A. Holt, R. A.Kenefick, L. C. Northcliff et al., Phys. Rev. D 39,3520(1989).

6. M. W. McNaughton, K. Koch, I. Supek, N. Tanaka,K. H. McNaughton, P. J. Riley et al., Phys. Rev.C44, 2267 (1991).

7. R. A. Arndt, J. S. Hyslop, and L. D. Roper, Phys.Rev. D35, 128 (1987).

8. J. Bystricky, C. Leluc, and F. Lehar, J. Phys. 51,2747(1990).

9. D. V. Bugg, Phys. Rev. C 41, 2708 (1990).10. D. V. Bugg and R. A. Bryan, Nucl. Phys. A 540,

449(1992).11. Y. Higuchi, N. Hoshizaki, H. Masuda, and H. Nakao,

Prog. Theor. Phys. 86, 17 (1991).12. N. Hoshizaki and T. Watanabe, Prog. Theor. Phys.

86,321 and 327 (1991).13. R. L. Shypit, D. V. Bugg, A. H. Sanjari, D. M. Lee,

M. W. McNaughton, R. R. Silbar et al., Phys. Rev.C40, 2203 (1989).

14. D. L. Adams, P. J. Riley, K. Johnston, and N.Davison, LAMPF Experiment 1097.

15. M. W. McNaughton and E. P. Chamberlin, Phys.Rev. C24, 1778 (1981).

16. M. W. McNaughton, B. E. Bonner, H. Ohnuma,O. P. Van Dyck, Sun Tsu-hsun, C. J. Hollas et al.,Nucl. lustrum. Methods A 241, 435 (1985).

17. A. J. Simon, Ph.D. thesis. University of Texas(1992).

18. E. Giilmez, A. G. Ling, C. A. Whitten, J. R.Amann, M. W. McNaughton, T. Noro et al., Nucl.lustrum. Methods A 297, 7 (1990).

19. E. Giilmez, S. Beedoe. T. Jaroszewicz, A. G. Ling.C. A. Whitten, M. W. McNaughton et al., Phys.Rev. C43, 2067 (1991).

20. M. W. McNaughton, K. Koch, I. Supek, N. Tanaka,D. A. Ambrose, P. Coffey et al., Phys. Rev. C 45,2564(1992).

21. J. S. Chalmers, W. R. Ditzler, T. Shima, H.Shimizu, H. Spinka, R. Stanek et al.. Phys. Lett.153B, 235 (1985).

22. D. V. Bugg and C. Wilkin, Nucl. Phys. A 467, 575(1987).

23. M. E. Beddo, G. Burleson, J. A. Faucett, S. Gardiner,G. Kyle, R. Garnett et al., Phys. Lett. 258B, 24(1991).

47



4He(TC+,pp)pn reaction at 500 MeVINSTITUTIONS: Univ. of Virginia, Arizona State Univ., James Madison Univ., Hampton Univ., Rensselaer Polytechnic

Institute

PARTICIPANTS: L. C. Smith (spokesperson), R. C. Minehart, D. Day, R. Lourie, R. M. Marshall, J. McCarthy, R. Sealock,S. T. Thornton, B. Ritchie, K. Giovanetti, K. Baker, and D. Tedeschi

Experiments have shown that a significant fraction ofpion absorption in nuclei occurs as a quasi-free two-bodyprocess involving T = 0 pn pairs. It is natural to askwhether this is a truly quasi-free version of the free K+ +d —> 2p reaction and to what extent the presence of othernucleons modifies this picture. Measurements'"^ of thetwo-body quasi-free angular distribution in ^He and 4He atenergies near the AU232) have revealed no quenching,enhancement, or distortion of the n+ + d —> 2p reaction,despite the substantially larger binding of the deuteron inthese isotopes. On the other hand, LAMPF measure-ments at 350 and 500 MeV on 3He have shown 15-30%enhancements in quasi-deuteron yield.9 We continuedthese high-energy measurements in Exp. 1126, using a4He target, where the binding energy per nucleon pair ishighest.

The experiment was conducted in 1990 at the P-̂ Echannel at LAMPF. Positive pions at 500 MeV (Ap/p =1.5%) were incident on a cylindrical 10-cm-thick liquid

4He target at 4.2 K with 0.00127-cm-thick Ni walls. Thebeam divergence was ±2°. Protons emitted from thetarget were momentum analyzed over an angular range of14-96° hy a 1-GeV/c magnetic spectrometer having a 30°bend and 1.82-msr solid angle. Momentum resolutionwas about 1.8% FWHM. The useable acceptance rangedfrom Ap/p = -25% to +50%.

Protons and neutrons were detected in coincidence bya movable array of two layers of 16 BC-408 10-cm x10-cm x 160-cm plastic scinlillator counters subtending asolid angle of about 240 msr at 2.8 m from the target.Mean-timing was used to determine time-of-flight toabout 600 ps FWHM and vertical position to about4.5 cm. Horizontal resolution was 10 cm. Sixteenoverlapping scintillation paddles 0.317-cm thick in front

of the array discriminated between charged particles andneutrons. All 96 timing and analog channels wereprocessed with fast ECL logic/delay and FERA CAMACmodules.

The pion flux was determined absolutely by using asampling grid scintillator to periodically measure beamflux and beam composition. The beam was constantlymonitored with an ionization chamber, calibratedfrequently against ' ' C activation. The angulardistribution for 7tp elastic scattering was measured withthe outgoing Tt and proton in coincidence as a systematiccheck of the apparatus and showed excellent agreementwith phase-shift parameterizalions of the VirginiaPolytechnic Institute group (Fig. 1).

The two particle detector arms were normallypositioned at the angles required to detect the two protonsfrom the K+ + d —» 2p reaction. For the 4He(7i+,pp,)pnreaction, measurement of P j and P 2 for the two protonspermits determination of the missing momentum P m andmissing energy Em of the unobserved pn pair. To isolatethe portion of phase space due purely to absorption, weplaced a cut on the square of the missing mass Ep, - P^,,for which the lower limit (allowing for energy resolution)eliminated the inelastic pion scattering events where thepion went into the bar, while the upper limit eliminatedevents with a missing mass greater than 2rrip + nip. InFig. 2, we show the missing energy distributions,without the 140-MeV pion cut. The contribution of pioninelastic scattering for missing mass greater than 140MeV is evident. After making the pion cut. we obtain thedistributions of events versus missing momentum shownin Fig. 3. The low-momentum peak is inierpreted aspredominantly two-body quasi-free absorption. The solidlines arc the results of a PWIA calculation of two-bodv

48


101

sr)

« 10°XX

d

D•o 10-

1

- . I j .

40

i i i I i i i

\

I I I I I I

60

9i,iab(deg)

I { I I I ! -

ArndtSM90 I

• This Experiment -

-

i i i i i

80 100

Fig. I. Measured Tip elastic cross section at Tn = 500 MeV compared to the cross section (solid line) obtained from the

SM90 phase-shift parameterizations of the Virginia Polytechnic Institute group.

4He (7t+,pp) pn Tn = 500 MeV

8, = 35°

0 100 300 0 100 300 0 100 300 0 100 300 0 100 300

Em (MeV)

Fig. 2. Missing energy distributions before eliminating events with missing mass more than 140 MeV greater than the ma.wof two line I eons.


10"

4He (7i+,pp) pn Tn = 500 MeV

0 100 300 0 100 300 0 100 300 0 100 300 0 100 300

Pm(MeV/c)

Fig. 3. Distribution of events versus missing momentum after eliminating events with missing mass more than 140 MeVgreater than the mass of two nucleons.

absorption using 4He wave functions given by Schiavilla,Pandharipande, and Wir inga 1 0 and normalizedindependently at each angle to match the peak height.Thus, in effect, we use the model only to determine thequasi-free peak shape at each angle. The excess ofobserved events relative to the calculated distribution athigher momenta is attributed to three- and four-bodyprocesses.

The area under these normalized two-body calculationsat each angle provides a differential cross section for quasi-free absorption shown in Fig. 4, along with our measure-ment of the differential cross section for 7t+ + d —> 2p.The curve through the 7t+ + d —> 2p data was obtainedfrom interpolation between published measurements atnearby energies. Agreement with our data is excellent,and when the curve is multiplied by 3.45, it is seen to fitthe quasi-free absorption data in ^He remarkably well,matching the angular dependence in detail. The quasi-freetwo-body absorption in 4He at 500 MeV is evidentlydescribed by the same partial wave mixtures used todescribe free absorption. The ratio. o^^Jod = 3.45,differs from the expected value of 3.0 (the number of T =0 pairs in 4He) by approximately the same factor as theratio, o^Jod. previously measured al 500 MeV, differs

300

"C^ 200.O

•§ 100

0

yfi Tn = 500 MeV S\

T \ 4He(!i*,pp)pn / \

*

ft tyjH(7t*,pp)l/ \

*

50 100 150

0i,cm (deg)

Fig. 4. Differential cross section for quasi-free absorptionin 4He (upper set oj data) and the differential cross sectionfor K+ + d —> 2p. The curve through the n+ + d —> 2pdata was obtained from interpolation between publishedmeasurements at nearby energies. The same curve scaledby a factor of 3.45 is plotted through the 4He data.

50

Research

from the expected value of 1.5. Thus, we can concludethat the different densities of the -̂ He and 4He seem tohave no effect.

References

1. D. Gotta, M. Dorr, W. Fetscher, G. Schmidt, H.Ullrich, G. Backenstoss et al., Phys. Lett. 112B,129(1982).

2. G. Backenstoss, M. Izycki, M. Steinacher, P. Weber,H-J. Weyer, K. Von Weymarn et al., Phys. Leu.137B, 329(1984;.

3. M. A. Moinester, D. R. Gill, J. Vincent, D. Ashery,S. Levenson, J. Alster et al., Phys. Rev. Lett. 52,1203(1984).

4. G. Backenstoss, M. Izycki, P. Salvisberg, M.Steinacher, P. Weber. H. J. Weyer et al., Phys. Rev.Lett. 55, 2782 (1985).


5. K. A. Aniol, A. Altman, R. R. Johnson, H. W.Roser, R. Tacik, U. Wienands et al., Phys. Rev.C33, 1714 (1986).

6. P. Weber, G. Backensloss, M. Izycki, R. J. Powers,P. Salvisberg, M. Steinacher et al., Nucl. Phys.A 501, 765 (1989).

7. P. Weber, J. McAlister, R. Olszewski, A. Feltham.M. Hanna, R. R. Johnson et al., Phys. Rev. C43,1553(1991).

8. S. Mukhopadhyay, S. Levenson, R. E. Segel, G.Garino, D. Geesaman. J. P. Schiffer et al., Phys.Rev. C43, 957 (1991).

9. L. C. Smith, R. C. Minehart, D. Ashery. E.Piaselzky, M. Moinester, I. Navon et al., Phys. Rev.C40, 1347 (1989).

10. R. Schiavilla, V. R. Pandharipande, and R. B.Wiringa, Nucl. Phys. A 449, 219 (1980).

51



Search for neutral pions from the spontaneous fission of252C f

INSTITUTIONS: Los Alamos National Laboratory, Rudjer Boskovic Institute, Abilene Christian Univ.

PARTICIPANTS: J. N. Knudson (spokesperson), C. L. Morris (spokesperson), J. D. Bowman, W. C. Sailor, S. J.Seestrom, I. Supek, M. E. Sadler, and L. D. Isenhower

Recent publications of theoretical work'-- by Ion,Ivaseu, and Ion-Mihai have raised the interestingsuggestion that natural pionic radioactivity occurring as abranch of spontaneous fission may be observable. Thisprocess, which is energetically possible for all nuclei withZ > 80, is not expected to be common, due to the fact thatmost of the fission Q-value goes into the kinetic energyof the fragments. This is a result of the Coulomb field atthe scission point. Thus, only a small fraction of theenergy released is available for exciting internal degrees offreedom in the fragments. The Bucharest group1 '2

combines the energetics with considerations of phasespace to conclude that the branch for pion emissionrelative to spontaneous fission is as large as 10~4 in someshort-lived nuclei.

These suggestions have given rise to several searchesfor neutral pionic radioactivity from spontaneous fission.No evidence for the process has been reported. Thesmallest upper limit reported is F^/Psf < IO~'- (95%C.L.)-5 by a group that ran deep underground. The nucleusmost often studied is 2 5 2 Q - J ^ ( 0 j t s availability.

We chose to conduct a search4 using the LAMPF 7C()

spectrometer^ which is well-suited for this experiment.It is not sensitive to particles that compete with the K'signal (particularly neutrons), and it is capable of handlingthe rates associated with a source strength of a fewmilliCuries. A schematic diagram of the active elementsof the spectrometer is shown in Fig. 1. The two armswere set with an opening angle of 180°. The distancefrom the center of the source to the first converter plane ofeach arm was 13.5 cm. A plastic scintillation detectorwas placed over the conversion planes in order to vetonear-zenith cosmic rays. The source consisted of

approximately KV9 (ig of ^-Cf encapsulated in a steel

The branching ratio is calculated using the relation

F s f ~ Nsf£caAQ (1)

where no is the number of neutral pions seen, ec is thespectrometer photon conversion efficiency for both arms,a is the total photon attenuation due to material betweenthe source and the detector, AQ is the solid anglesubtended by the spectrometer, and Nsf is the total numberof spontaneous fissions in the source.

A Monte Carlo calculation that incorporates allaspects of the 7t° detection process was used to determinethe solid angle for energetic n(h. The unusual spectro-meter configuration yielded an acceptance of 13.5% of 47tfor 7i s that decay at rest. The calculation also predicted anenergy resolution of about 4 MeV (FWHM) for low-energy (<10 MeV) 7i°s.

The experiment was set up in the P E cave during anextended maintenance period. Data were collected for 354hours source-out and 893 hours source-in. The averagetrigger rate was 0.08 Hz. In order to optimize thedetection of low-energy 7t()s, stopping 7i~ data werecollected during the final days of accelerator operationprior to the experiment. These data were analyzed andinspected for cuts that could be applied to the fission datato reject backgrounds.

The net result of the search was -0.3 ± 10.3 events.The triggers seen were primarily accidental coincidencesbetween cosmic rays that missed the veto detectors. Weconclude that no excess rate of n° production was seenabove the background. An analysis6 based on Poissnn

52


Fig. 1. Side view of the experimental arrangement. The source S is surrounded bv 5%-boron-loaded polvethvlene shieldingB. The two arms of the spectrometer are symmetric about the source: various elements arc identified on one side only forclarity. The various veto counts V are in front of and over the photon converters. The Pb-gtass elements of the spectrometerare the converters C and the calorimeters L Multiwire proportional chambers M lie between each converter and its triggerscintillator T. A polvethvlene sheet N lies in front of each arm to degrade neutrons and charged panicles.

statistics gives an upper limit on the number of detectedn^s of no < 10.2 with a 90% confidence level. Since anenergetic 7t° created during spontaneous fission wouldneed to penetrate an even larger potential barrier than onecreated at r^st, we assume that any rc'^ yield would beconcentrated at 0 MeV. This assumption allows us to usethe solid angle for 0 MeV 7t°s in Eq. (1). We calculate anupper limit to the branching ratio for 7t°s emitted fromspontaneous fission to be

* < 1.37 x lO"1 ' (90% C.L.) ,

r(2)

which is in agreement with the work of Ref. 3.

References

1. D. B. Ion, M. Ivascu, and R. lon-Mihai, Ann. Phys.(N.Y.) 171. 237 (1986): Rev. Roum. Phys. 31. 205

(1986); 31. 209 (1986); 31, 551 (1986); 32, 299(1987); 32, 1037 (1987); 33, 239 (1988).

2. D. B. Ion, R. Ion-Mihai. and M. Ivascu, Rev. Roum.Phys. 33, 1071 (1988).

3. J. Julien, V. Bellini, Y. Cassagnou, C. Cerruti, J.M. Hisleur. R. Legrain, and B. Lucas. Z. Phys. A332. 473 (1989).

4. J. N. Knudson. C. L. Morris. J. D. Bowman. W. C.Sailor, S. J. Seestrom, I. Supek, M. E. Sadler, andL. D. Isenhower. Phys. Rev. C 44. 2869 (1991).

5. H. W. Baer. R. D. Bolton, J. D. Bowman. M. D.Cooper. F. H. Cverna, R. H. Heffner et al.. Mir/.Instmm. Methods 180, 445 (1981).

6. G. Zech. Nucl. lustrum. Methods A 111. 608(1989).


EXPERIMENT 1190 - P3West

Pion-proton partial total cross sections from 60 to 200 MeVINSTITUTIONS: Univ. of Colorado, Los Alamos National Laboratory, Univ. of British Columbia, Univ. of Minnesota,

California State Univ.

PARTICIPANTS: J. T. Brack, E. F. Gibson, S. Hoibraten, M. Holcomb, M. D. Kohler, J. J. Kraushaar, B. J. Kriss, J. L.Langenbrunner, C. L. Morris (spokesperson), S. P. Parry, R. A. Ristinen (spokesperson), A. Saunders,W. R. Smythe, and R. M. WhiUon

The group of Friedman et al., working at TRIUMF,has introduced a new method of using partial total-cross-section measurements to compare pion-proton crosssections to those calculated from phase-shift programs. Inthree publications '"•* over the past two years, they reportno significant discrepancy between their results from 45 to202 MeV and the predictions of the popular phase-shiftprograms. This agrees with the results of five jt+pdifferential cross-section measurements.4"8

This is in contrast to the findings of several otherstudies of differential cross sections for 7i+p elasticscattering in the same energy range,9"15 which have all

reported differential cross sections substantially below thephase-shift calculations.

In an attempt to resolve the discrepancy between thepartial total measurements and some of the differentialmeasurements, the present work was undertaken at theP-̂ W channel at LAMPF. The liquid hydrogen targets andscintillator system used for the experiment were designedand constructed by LAMPF personnel.

The pion beam incident on the target was defined bytwo 1-cm-diameter in-beam counters. Pion identificationis shown in Fig. 1, a plot of the TDC between the in-beam counters versus a TDC started by one in-beam

1250

1225

1200

1175

1150

1125

1100600

1 rJn = 60 MeV

I i

620 640 660

S r S 2 TDC680 700

Fig. I. Beam particle identification at a pion energy of 60 MeV. The horizontal axis is the time difference between the in-heam counters; the vertical axis is the particle flight time through the beam channel to one of the in-beam counters, referencedto the accelerator rf signal. The pion and muon groups are wrapped around several times relative to the electron group.

54


counter and stopped by a signal from the accelerator rf.Beam energy was calibrated to better than ±1 MeV bytime-of-flight over flight paths of up to 10-m length.

The liquid hydrogen targets were vertical cylinders of3.5-cm diameter and 6.0-cm diameter, contained in avacuum box with Mylar entrance and exit windows. Thetarget thicknesses were determined to be within about 1 %of the nominal value by use of a specially designed, eight-element range spectrometer.

Pions scattered outside a 30° forward cone wereindicated by logic conditions on the various counters inthe system. Those inside the cone were identified andseparated from recoil protons by cuts on the two-dimensional diagram of pulse weight versus time-of-flightin a counter subtending the 30° forward cone.

The essential figure of merit for this system is theratio of observed partial total pion scattering eventsoutside of 30° with a full target to that for the emptytarget. At 60 MeV, this ratio was 2.5; at 174.5 MeV, itwas 4.3. Under these conditions we had only to measure afour-fold difference in scattering rate to a few percentaccuracy in order to achieve the goals of the experiment.

Our preliminary results at 21 pion energies from 60to 260 MeV are consistently below the predictions of boththe KH80 (see Fig. 2) and SM90 phase-shift solutions.Our results are not yet corrected by Monte Carlocalculations. Our early estimates of these caculationssuggest that they will be no larger than a few percent.Thus, our measured values of the partial total crosssections appear to be significantly smaller than the phase-shift predictions.

co 1.2

Si3OCO

OoCO

X

• = 1 . 1

1.0

I 0.9

Q.

UJ 0-8

• Friedman Integral Measurements, 1989,90,91• Colorado / LAMPF E1190 Integral Measurement* 1991

•Preliminary Results

50 100 150 200

TB(MeV)

250 300

Fig. 2. The ratios of the integral cross sections outside of 9K = 30° relative to the KHSO phase-shift solutions integratedover the same angular range. The Friedman integral measurements are from Refs. I, 2, and.?.

References

1. E. Friedman. A. Goldring, G. J. Wagner, A. Altman,R. R. Johnson, O. Meirav. M. Hanna. and B. K.Jennings, Phys. Lett. ,8 231, 39 (1989).

2. E. Friedman, A. Goldring, G. J. Wagner. A. Altman.R. R. Johnson, O. Meirav. and B. K. Jennings, Nucl.Phys. A 514, 601 (1990).

3. E. Friedman. A. Goldring, R. R. Johnson, D.Vertterli. J. Jaki. M. Metzler. and B. K. Jennings,Ph\s. Lett. B 254, 40 (1991).

4. P. J. Bussey, J. R. Carter. D. R. Dance. D. V. Bugg.A. A. Carter, and A. M. Smith. Nucl. Phys. B 58,363(1973).

5. P. Y. Berlin, B. Coupat. A. Hivernot. D. B. Isabelle,J. Duclos. A. Gerard et al.. Nucl. Phys. B 106. 341(1976).

6. B. G. Ritchie, R. S. Moore. B. M. Preedom, G. Das.R. C. Minehart. K. Gotow. W. J. Burger, and H. J.Ziock. Phys. Lett, li 125. 128 (1983).


7. C. R. Ottermann. E. T. Boschitz. W. Gyles. W. List.R. Taeik. R. R. Johnson. G. R. Smith, and E. 1..Mathie. Pins. Rev. C 32. 928 (1985).

X. C. Jorani et al.. contribution to nN Newsletter. No. 2I May 1990).

9. E. G. Auld. D. Axen. J. Beveridge. C. Duesdieker. L.Kelawka. C. H. Q. Ingrain et al.. Can. J. Pins. 57.73(1979).

10. J. S. Frank. A. A. Browman. P. A. M. Gram. R. H.Heftner. K. A. Klare. R. E. Vlischke et al.. Pins.Rev. D2H. 1569 H983).

11. I . VViedner. K. Goring. J. Jaki. U. Klein. W. Kluge.H. Matthiiv et al.. Phx\. Rev. Lett. 58. 648 (1987).

12. J. T. Brack. J. J. Kraushaar. J. H. Mitchell. R. J.Peterson. R. A. Ristincn. J. L. L'llmann el al.. Pins.Rev. C34. 1771 (1986).

13. J. T. Brack. J. J. Kraushaar. D. J. Rilett. R. A.Ristinen. D. K. Otteuell. G. R. Smith. R. G.Jeppesen. and N. R. Stevenson. Pins. Rev. C 38.2427(1988).

14. J. T. Brack. R. A. Ristinen. J. J. Kraushaar. R. A.Loveman. R. J. Peterson. G. R. Smith et al.. Phw.Rev. C41. 2202 (!990).

15. M. Met/ler et al.. contribution to nM Newsletter.No. 2 (May 1990).

56



MEGA: Search for the rare decay JI+ —> e+yINSTITUTIONS: UCLA, Univ. of Chicago, Fermilab, Hampton Univ., Univ. of Houston, Indiana Univ., Los Alamos National

Laboratory, Queens Univ., Stanford Univ., Texas ASM Univ., Valparaiso Univ., Univ. of Virginia,Virginia Polytechnic Institute

PARTICIPANTS: B. M. K. Nefkens, B. Tippens, S. C. Wright, P. S. Cooper, K. Baker, L. Tang, M. Barakat, Y. Chen, M.Dzemidzic, J. Flick, E. V. Hungerford III, K. Lan, B. W. Mayes II, L. Pinsky, W. von Witsch, J. Knott, K.Stantz, J. Szymanski, J. F. Amann, R. D. Bolton, S. Carius, M. D. Cooper (spokesperson), W. Foreman,R. Harrison, G. Hart, G. E. Hogan, N. June, D. Kercher, T. Kozlowski, M. A. Kroupa, R. E. Mischke, F. J.Naivar, J. Novak, M. A. Oothoudt, C. Pillai, S. Schilling, J. Sturrock, D. Whitehouse, A. Hallin, E. B.Hughes, C. Gagliardi, G. Kim, F. Liu, R. E. Tribble, X. Tu, L. Van Ausdeln, X. Zhou, R. J. Fisk, D. D.Koetke, R. Manweiler, S. Stanislaus, W. Stephens, B. Wright, K. O. H. Ziock, and L. E. Piilonen

The search for n. -> ey at LAMPF is called MEGA,an acronym standing for Muon decays into an Electron anda GAmma ray. and is an experiment with a branching-ratio sensitivity of roughly 10" '^ . Such a search isimportant because there is no known need for conservationof muon family number, though the observation of thedecay would indicate the need for an extension to theStandard Model of electroweak interactions. The year1991 has been used to complete the R&D phase of thedevelopment, as well as much of the construction. ByMarch of 1992, the components (except for the last pairspectrometer) will be built, and assembly will begin fordata taking in 1992. The first Ph.D. has been awarded toa student from MEGA, and some of the interesting resultswill be given below.

The MEGA apparatus is shown in Fig. 1. Theapparatus is contained in a large solenoidal magnet with a1,5-T field, a clear bore of 1.85 m, and a length of 2.9 m.The required muon stopping rate is 3 x l()7 Hz (average).The detector is divided into a positron spectrometer and aseries of photon pair spectrometers. All of" the chargedparticles arising from muon decay are confined by themagnetic field to a maximum radius of 29 cm, leaving thephoton detectors in a relatively quiet environment.

The positron arm consists of two parts: scintillatorsfor liming and a set of multi-wire proportional chambers(MWPC) for momentum determination. The .scintillatorsare ready for mounting on the lead shielding that alsoserves as their support. The MWPC design for thepositron spectrometer is called "Snow White and the

Seven Dwarfs." "Snow White" is the central, cylindricalchamber of 11.25-cm radius whose cathodes are relativelyclean. The cathodes are active only in the low-rate portionof the spectrometer over the lead beam pipe. Seven small"dwarf" chambers encircle Snow White to provide thenecessary redundancy for pattern recognition. Thecomponent of momentum perpendicular to the field ismeasured by the wire hits, and the parallel component ismeasured from the induced pulses on the cathodes, whichcontain stripes that spiral relative to the wires.

A difficult problem in the chamber performance hasbeen "current mode." Current mode is the flow ofmicroamperes of dark current that is induced by radiation,but is persistent after the source is turned uff. Theexperimental design for the chambers called for 1-mmspacings between wires, 15-nm wire diameter, and a 1.75-mm half-gap; this geometry yields a plateau voltage of2400 volts. It has been found that current mode can beeliminated by opening the wire spacing to 1.3 mm andadding 0.2% water to the gas mixture as a quencher. Theopening of She wire spacing reduced the plateau voltage to2150 volts but has little effect on the chamber resolutionbecause multiple scattering contributes in quadrature to theposition uncertainties. The eight chambers, most ofwhich are complete, use the new wire spacing.

The bladders, inflatable gaskets that look like smallinner tubes, make the gas seals between the wire chambersand the other apparatus of the detector. Originally made oflatex, the bladders were showing signs of rot after a year.Switching elastomers to neoprenc. which is much more


PhotonSpectrometer

PositronSpectrometer

Pair

Beam

TimingScintillators

Fin. I- A simplified cutaway view of the MEGA apparatus. The detector is mounted inside a superconducting solenoid witha 1.5-T field. The muons enter along the magnetic field and stop in the target. Positrons from mcum decays are delected in theeight cylindrical wire chambers and the cylindrical arrays of scintillators surrounding the beam pipes. The three largecylinders are pair spectrometers for photon detection.

rc:;istant to chemicals and light, seems to have eliminatedthis concern.

The cathodes of the chambers are supported bydifferential gas pressure with helium on one side andchamber gas on the other. From the point of view of thesystem to supply the needed gases, the array of chambers

looks like a set of 17 coupled balloons. To properlymaintain the pressures requires an apparatus of somecomplexity. One of the unexpected events of 1991 waswhen this complex gas system got cross wired, reversedthe pressure across the foils, and destroyed three chambers.In order to prevent a recurrence of such an accident, a

58


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10

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h

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20 40 60 80 ' 0

Track Incident

MC Anode

-

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I ) • l • l •» l •I [ I I 1

Cathode

B o a D o

DDDDDDo ••n a • n • Q - ?

20 40 60 80 '

Angle (deg)

Fig. 2. Anode and cathode hit multiplicities as a functionof the incident angle of the track for data and simulatedevents. The average multiplicities are shown in theprofile on the right of each plot.

review of the gas system was convened and steps are beingtaken to greatly improve its reliability. Some of thosesteps include better procedures, more testing, newhardware to prevent reverse pressurization, and correctingfor atmospheric pressure changes with the high voltagerather than with the gas.

Ultimately, the electron chambers will be used in thevery high rate environment given by the 3 x 107 Hz(average) of stopping muons. The Monte Carlo (MC)simulation has predicted that pattern recognition can beaccomplished in such an environment. Some results fromthe thesis work of Charles Jui, based on data taken in1990 with Snow White (2-mm pitch) and one dwarf(1-mm pilch), suggest that this simulation is remarkablyaccurate. Figure 2 shows a comparison between the dataand MC for the multiplicity of hits as a function of angleof incidence on the chamber for both the anodes andcathodes. The agreement supports the prediction for thefraction of struck wires or cathode strips for an averageevent. The position resolution of the chambers is verifiedby looking at the residuals for reconstructed tracks; theresiduals are the difference between the predicted position

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0.0 0.5 1.0

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Fig. 3. Comparison of experimental and Monte Carlodistributions for the difference between projected and actualcoordinates of hits in Snow White.

of a chamber crossing and the measured one. Thosevalues and their agreement with MC are shown in Fig. 3.The fraction of reconstructible events as a function of rateis a measure of the accuracy with which accidentals, themain background for n + -» e+y, are predicted. Theagreement with the MC is given for a random trigger inFig. 4. The rates could not be taken above 70 MHz(instantaneous) because of current mode. The behavior ofSnow White up to 300 MHz showed no surprises. Theenergy spectrum of these electrons from a random triggeris shown in Fig. 5. Qualitatively, the spectrum lookslike what would be expected from normal muon decay.The MC fits the shape well in detail. That MCcalculation can be used to predict the response function forthe spectrometer, as displayed in Fig. 6. The resolution isaround 600 keV FWHM. With the full complement ofchambers, there is every reason to believe the 300-keVdesign will be reached.

The photon arm is three concentric pair-spectrometersof essentially identical construction. Plans for a fourth

59


Inst. \i Stopping Freq. (MHz)

Fig. 4. Plot of the number of reconstructed backgroundtracks per 1000 triggers versus the instantaneous beamrate. The Monte Carlo simulations are shown with thefilled squares.

layer have been dropped. The inner two, which are justbeing completed for 1992 data taking, are as originallydesigned. A magnified cross section of one is drawn inFig. 7. Each pair spectrometer is made of lead converters,MWPCs, drift chambers, and scintillators. The third onewill have the outer radius expanded and an extra row ofdrift chamber wires added to increase the acceptance forhigh-energy gamma rays. This increased capability isextremely useful in determining the energy responsefunction from the decay rc° -> yy, if the TC° is made fromstopping pions via 7i~p —> 7t°n; the energies of the twogamma rays ranges from 55 to 82 MeV.

The construction of the cylindrical laminates thatmake up the mechanical supports for the converters andchambers has become a viable technique. All cylinders forlayers 1 and 2 are complete and have been assembled intothe end plates. The delay lines discussed below have beenmounted on both layers. The layer-2 wires are strung andthe chambers tested at high voltage, performing as well asthe prototypes that meet specifications. Layer 1 is beingwired. The layer-3 cylinders and end plates for use in1993 are beginning fabrication. All scintillators and theirlight guides are complete.

The measurement of track coordinates parallel to theaxis of the cylinders will be mude with I-cm by 180-cmlong delay line strips with a factor of 40 time expansion.Manufacturing difficulties have caused the delay lines tobe made in two pieces that are joined at the middle of thechamber. The full-length strips have been tested in a

Reconstructed Energy (MeV)

Fig. 5. A comparison of the energy spectra frombackground muon decays for data and Monte Carlo.

Fig. 6. The distribution of reconstructed energy forsimulated 52.8-MeVpositrons using the same parametersas the simulation for Fig. 5. The dashed line is located at52.8 MeV, and the shift of the peak is due to energy lossin the detector elements.

chamber and shown to a give 5-mtn resolution that isconsistent with the requirements of the experiment. Thejoint at the middle is hardly noticeable in a linearity plotof position versus time.

The measurement of accidentals in the pairspectrometers has caused some reworking of themultiplexing of the photon-arm readout. The geometricalinformation from the trigger as to where the conversiontook place will be fed back to the electronics to enableonly the readout channels in the region of the photon

60


Photon Arm Event

52.8 MeV y

Aluminum— Delay read out

X

O

X

O

1 x

O

f x

Lo

UX

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o

o

o

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o

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3MeV

f 17 MeV

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Scintillator RohacellLead

Fig. 7. A highly magnified schematic of the elements of the pair spectrometers.

shower. This scheme will prevent the overwriting ofuseful data by accidental hits in another part of thedetector. The electronics to accomplish the signalprocessing and multiplexing are complete. The delay linepreamplifiers and time pick-off circuits are still underconstruction.

Preliminary analysis of photon spectra taken in 1990shows no surprises. The pattern recognition algorithmsare being made more sophisticated so that good spectra canbe obtained. The reconstruction efficiency is alsonominal.

The trigger for MEGA is a high-energy gamma ray.Pattern recognition is done in hardware using equationswritten into programmable array logic. The equationshave their origins in Monte Carlo simulations and datafrom the 1990 running. Each photon layer has two

stages, one that has a 30-ns propagation delay and controlsthe multiplexing, and one that is more sophisticated buttakes 300 ns. The second stage for layer I was availablein 1990 and worked well. The final three modules, onefirst stage for each layer and one second stage for layer 2.are at the board houses. Similarly, a multi-layer routingbox, for shipping gale signals to appropriate destinationsfor the different triggers, is also in assembly. The fewremaining gale fan-outs and busy controllers are nearingcompletion.

The on-line software filter requires considerablecomputer power. The programing necessary toincorporate four DECstation 5000/200 microprocessorshas been finished and tested. The high-speed VMEinterface properly transferred data at 12 Mbytes/sec, severaltimes the need. Four processors are about twice the


computing power required by the design with two pair In the next year, all of the detector except the

spectrometers. outermost pair spectrometer will be installed. With theThe final type of FASTBUS module, the ADC, has limited beam time available, a branching ratio sensitivity

been delivered by the manufacturer. It has a somewhat of about 5 x 10~12 in 1992 is expected; this plan allowsslower settling time after a fast clear than specified, but for careful setup before the turn on of beam. Final datahas been deemed adequate for MEGA. All ordered taking, expected in 1993 and 1994, will make anotherFASTBUS modules have been delivered. factor of ten improvement in sensitivity.

62


EXPERIMENT 1054-SMC

Ultra high precision measurements on muonium groundstate: hyperfine structure and muon magnetic momentINSTITUTIONS: Yale Univ., Univ. of Heidelberg, Syracuse Univ., Los Alamos National Laboratory, Brookhaven National

Laboratory

PARTICIPANTS: A. Ahn, B. Boshier, D. Ciskowski, S. Dhawan, X. Fei, V. W. Hughes (spokesperson), M. Janousch, W.Liu, K. Jungmann, G. zu Putlitz (spokesperson), B. Matthias, W. Schwarz, R. Holmes, P. Souder(spokesperson), J. Xu, C. Pillai, O. van Dyck, and K. Woodle

Goals of Experiment

1I) Measure the ratio of the magnetic moments of muonand proton. u.n/Mp. with a fractional accuracy of 50 to70 parts per billion (ppb).

(2) Measure the muonium hyperfine structure interval inthe ground state. A v , to 10 ppb. Thesemeasurements will improve our knowledge ofand of Av by a factor of about 5.

Scientific Importance

The present experimental value for Av from ourearlier LAMPF experiment on muonium is: '-2

Avexp = 4 463 302.88 (16) kHz (36 ppb) . (1)

and for u.jj/u.p is:

| i u / | i p = 3.183 346 1 (11) (360 ppb). (2)

The present theoretical value for Av is:

Avlh = 4 463 303.11 kHz (400 ppb) , (3)

in which the principal uncertainty arises from theuncertainty in Hu/|ip. The experimental and theoreticalvalues for Av agree well:

Av l h - A v e x p = 0.23 (1.7) kHz (4)

(5)

The important scientific implications of the newLAMPF Exp. 1054 are the following:(1) It will improve substantially on one of the most

sensitive tests of QED for the e-|i interaction in thetwo-body bound state and of the behavior of the muonas a heavy electron.

At present the calculation of the higher-ordercontributions to Av has been done to 220 ppb andcan with further work be carried to 20 ppb. With theimproved accuracy in Jiu/(ip from LAMPF Exp.1054, the theoretical value for Av could be at aboutthe 50-ppb level. Hence, Avth and AveXp could becompared at about the 50-ppb level.

(2) Determine the fine structure constant a at the 25-ppblevel.

This is done by equating Av (h to A v e x p

treating a as the variable to be determined in Av]n.Such a precision would be equivalent to (he aobtained from the quantized Hall effect and wouldallow a test of the theory of ge-2 for the electron bycomparison with the experimental value for g c-2.independent of condensed matter theory.

(3) Most precise determination of fundamental propertiesof muon, | i u and mu .

The muon mass | j u is obtained from the relation

mH_gu|ipMBme 2 u.u n p

(6)

A v , h - A v c x p = ( ( ) ( ) 3 ± ( ) 4 ) p p m

where Hu/|ip is now the least well-known quantity.The muon mass m^ is needed for the interpretation ofprecise spectra of muonic atoms and for thedetermination of mVM. | i u / | ip is needed for thedetermination of gjj-2 from (he new Brookhavenmuon g-2 experiment.

ft 3


Method of Experiment

LAMPF Exp. 1054 basically is a microwave speelro-scopy experiment, similar in principle to our previousexperiment, which observes the induced magnetic dipoletransitions indicated in Fig. 1 at a magnetic field H -18 kG. The relevant Hamiltonian is

H = a?M 7 "H - H

a/h = Av - 4 463 MHz

and the magnetic hyperfine coupling constant a andare the quantities determined. The symbols in Eq. (7)have their usual meanings as in Rets. I and 2:specifically. Iu is the muon spin operator and J is theelectron total angular momentum operator.

The factors of improvement in LAMPF Exp. 1054 uscompared to the previous experiment are the following:

(1) Muon Beam: A separated, high purity | i + beam withan intensity increase by about a factor of 3.

(2) Magnetic Field: A more homogeneous, stable, andstronger (-18 kG) magnetic field provided by acommercial MRI magnet operating in persistentmode.

(3) A chopped muon beam that will allow line-narrowingby observing transitions only for long-livedmuonium atoms.

The resonance lines will be observed by sweeping themagnetic field through the resonance. This will beachieved by modulating the main MRI solenoid field withan independent solenoid inside the MRI magnet.

An integrating scintillation muon counter willmonitor the incoming fi+ beam and scintillation countersdownstream of the gas target will detect the decaypositrons.

1

8

6

4

2CO

-2

-4

-6

-8

C

D 2 4 6 8

-

-(F, MF)

-

i^^^TCo)

---) 2 4

101 i

^ ^2

4

i

6

H(kG)12 14 16 18 20 22 24

i | , | , | ,

Mj, MM

1 i ' i • i •

i ^^^(1/2, 1 / 2 ) ^ ^ ^ ^ " ^

(1/2,-1/2)

(-1/2, -1/2)

(-1/2,1/2)^^:i

I , ! , I i I , I

8 10 12 14 16X

Fig. I. Hreit Ruhi energy level diagram for muonium in iis I~S 1/2 ground slate in a magnetic field.

Research

Progress and Status of Experiment

Magnet

We have obtained and successfully powered oursuperconducting solenoid to a field to 1.7 T. The magnetis a 2-T MRI solenoid (shown in Fig. 2) by OxfordMagnet Technologies. The magnet will operate at 1.85 Tin the persistent mode. A separate solenoidal coil insidethe bore will modulate the field by up to 0.02 T toobserve a resonance line.

A magnetic shield design has been completed for thesolenoid. The shield will protect the experimental


personnel and environment from the high fringe fieldsproduced while protecting the homogeneous internalvolume from stray external magnetic fields. The shielddesign calls for four walls of 5" thick steel. Two of thewalls will be 10' tall and 10' wide to form the endcaps.Each endcap will have a 4' diameter hole through its centerto allow access to the solenoid. The remaining two wallswill be 10' high and 15' long. This will allow 3' ofclearance between the ends of the solenoid and the endcaps.Flux density in the steel is designed to be less than 1.3 Tat all points.

The solenoid was successfully shimmed to 10 ppmover a 30-cm diameter spherical volume while at the

Fit;. -• Supercoiuluvlini; solenoid for Exp. 1054: The ulna hi ah prevision measurements on mnoniiim ground stole,hyperfinc structure and union magnetic moment.


manufacturer's. The solenoid will be shimmed on site tothis same homogeneity when construction of the shield isfinished.

Beam Line

Several tests were conducted of the beam line layoutand elements. These tests included measurement ofchopper rise and fall times, background levels caused bythe chopper and separator, intensity measurements, and thebeam optics effects of the solenoid. Results of thesetests, together with beam line simulation calculations,determined the configuration of our apparatus. It wasfinally decided to include a 45 ' bend following the chopperto reduce background and to increase the distance fromother users in the SMC. This site is being prepared forthe 1992 run cycle.

Chopper

We have studied the chopped muon beam for theexperiment. The SMC chopper consists of two plates,each 1 m long with a 10-cm gap. A voltage of ±20 kV isapplied to the plates. The rise time of the voltage isabout 100 ns and the fall time is 120 ns. The maximumrepetition rate is 72 kHz. For our experiment, the \i +

beam is transmitted with the chopper field off. With thechopper field on. the | i + beam does not enter ourapparatus. Satisfactory production and operation of achopped [i+ beam were obtained.

Calculations

Several calculations have been tarried out for thisexperiment. We have calculated the dependence of thefractional precision ;>f Hn/nip uPor< the precision of themagnetic: field measurement. The microwave cavitymodes were investigated. The line shapes and line widthsof the resonance curves of the Zeeman transitions for bothnormal and "old muonium" methods and for variousmicrowave powers were studied.

Plans and Schedule

As a goal, we plan to have enough of the apparatusready so that we could usefully take muon beam insummer 1992. As a minimum, we would study the muonbeam into our apparatus and. as a maximum, we wouldtry to observe a resonance signal (but not a sweptresonance line). Data taking is planned in 1993.

References

1. F. G. Mariam. W. Beer. P. R. Bolton. P. O. Egan.C. J. Gardner. V. W. Hughes el al.. Pins. Rev. Let!.49. 993 (1982).

2. V. W. Hughes and G. zu Putlit:-. in QuantumElectrodynamics, T. Kinoshita. Ed. (World Scientific.Singapore. 1990). p. 822.

66



New search for the spontaneous conversion of muonium toantimuoniumINSTITUTIONS: Yale Univ., Univ. of Heidelberg, College of William & Mary, GSI Darmstadt, Paul Scherrer Institute,

Brookhaven National Laboratory

PARTICIPANTS: B. E. Matthias, H. E. Ann, F. Chmely, V. W. Hughes (spokesperson), Y. Kuang, S. H. Kettle, H.-J.Mundinger, B. Ni, H. R. Schafer (spokesperson), K. P. Jungmann, G. zu Putlitz, M. Eckhause, J. R.Kane, M. T. Witkowski, H. Orth, A. Badertscher, and K. A. Woodle

A new search for spontaneous conversion ofmuonium to antimuonium was completed and the resultsare published.'

Muonium was formed in a SiCb powder target andthermal muonium diffused into vacuum downstream of thetarget. A new signature for M —> M conversion with lowbackground was implemented that required the coincidentdetection of the decay products of the antimuonium atom,the energetic e~ and the atomic e+ A schematic view ofthe apparatus is shown in Fig. I.

The most probable number of M events was found tobe zero, with a 90%-confidence-level upper limit of 2counts. The resulting upper limit on the probability forthe M to M conversion per atom is Pjvf < 6.5 x 10~7

(90% C.L.). This gives an upper limit of G M M < ° ' 6

Gp (90°/c C.L.) on the effective four-fermion couplingconstant for M —> M conversion.

Many theoretical discussions of M —> M conversionhave been given, often in terms of a multiplicative law ofmuon number conservation. Our result provides arelevant constraint on the left-right symmetric models.~

Electron Collection

Access Window Target Bending Magnet

MicroChannel Plate

Bellows

Fig. I. Schematic view of the apparatus. Beam counterand target were mounted at 50° with respect to the incidentmuon beam.

References

1. B. E. Matthias, H. E. Ahn, A. Badertscher, F.Chmely, M. Eckhause, V. W. Hughes et al., Phys.Rev. Lett. 66, 2716 N991).

2. P. Herczeg and R. N. Mohapatra, "Muonium toAntimuonium Conversion and the Decay | i + -»

e+v evu in Left-Right Symmetric Models," in Proc.of the Vancouver Meeting. Particles and Fields VI,Vancouver, August 18-22, 1991. D. Axen et al., Eds.(World Scientific, 1992), Vol. I, p. 572: and in LosAlamos National Laboratory document LA-UR-92-2089 (submitted to Physical Review Letters. 1992).



RHO: Measurement of the Michel parameter p with theMEGA positron spectrometerINSTITUTIONS: UCLA, Univ. of Chicago, Fermilab, Hampton Univ., Univ. of Houston, Univ. of Indiana, Los Alamos

National Laboratory, Queens Univ., Stanford Univ., Texas A&M Univ., Valparaiso Univ., Univ. ofVirginia, Virginia Polytechnic Institute

PARTICIPANTS: B. M. K. Nefkens, B. Tippens, S. C. Wright, P. S. Cooper, K. Baker, L. Tang, M. Barakat, Y. Chen, M.Dzemidzic, J. Flick, E. V. Hungerford III, K. Lan, B. W. Mayes II, L. Pinsky, W. von Witsch, J. Knott, K.Stantz, J. Szymanski, J. F. Amann, R. D. Bolton, S. Carius, M. D. Cooper (spokesperson), W. Foreman,R. Harrison, G. Hart, G. E. Hogan, N. June, D. Kercher, T. Kozlowski, M. A. Kroupa, R. E. Mischke(spokesperson), F. J. Naivar, J. Novak, M. A. Oothoudt, C. Pillai, S. Schilling, J. Sturrock, D.Whitehouse, A. Hallin, E. B. Hughes, C. Gagliardi, G. Kim, F. Liu, R. E. Tribble, X. Tu, L. Van Ausdeln,X. Zhou, R. J. Fisk, D. D. Koetke, R. Manweiler, S. Stanislaus, W. Stephens, B. Wright, K. O. H. Ziock,and L. E. Piilonen (spokesperson)

The high performance capabilities of the MEGApositron arm are well suited to study the properties of thenormal decay of the muon. The muon decay rate is givenby

x-dxd(cos9)=3(1 -x) + 2f (4x-3)3

+ Pu£ cos9 [ 1 - x + y (4x -

where x = E e /E m a x , 6 is the angle between the electrondirection and the muon spin; p, 5, and \ are Michelparameters; and P^ is the average muon polarization. Thecurrent measured value for p is 0.7518 + 0.0026. TheStandard Model makes definite predictions for p, 8, andPuq of 0.75. 0.75. and 1.0, respectively; these values canbe tested with precision measurements. Any deviationfrom these values from their predictions would be anindication of new physics. For example, in a left-rightsymmetric model, the mixing angle £ between the left-and right-handed intermediate vector bosons is

The MEGA detector has large solid angle, isazimuthally symmetric about the beam and target, and isthe same upstream and downstream of the target. Thesefeatures allow the statistical and systematic errors to becontrolled in making a measurement. A careful MonteCarlo simulation was done to understand the methods forminimizing the errors. One significant observation wasthat the acceptance between 0.75 < x < 1.0 is constant to5% for events making 1, loops in the magnel. Thisregion of x is where the spectrum is most sensitive to p.The result of the investigation is that p can be determinedwith a precision of 0.0008 in a two-week data-takingperiod during the summer of 1992.

As part of the 1990 engineering run for MEGA, somelimited data were taken on normal muon decay with twowire chambers. The reconstructed energy spectrum isshown in Fig. 1. The resolution is degraded by anunfortuiiate choice of trigger scintillators. The solid curveis a Monte Carlo simulation assuming p = 0.75. When pis allowed to vary, the value is p = 0.758 ± 0.013 (stat) +0.010 (syst). With a complete, symmetric detector andmore beam time, the errors can be reduced considerably.


5000

4000

tn 3000

IJ 2000

1000

0

Data

MC

TTTT

30 35 40 45 50 55 60

Reconstructed Positron Momentum (MeV/c)

Fig. I. Momentum spectrum of positrons from the normal decay of the muon. The solid curve is from a Monte Carlo

simulation assuming p = G. 75.


EXPERIMENT 1208 - WNR

Neutron-proton bremsstrahlung studies at LAMPF/WNRINSTITUTIONS: Los Alamos National Laboratory, Lawrence Livermore National Laboratory, ISN-Grenoble (France),

Univ. of Saskatchewan (Canada)

PARTICIPANTS: S. A. Wender (spokesperson), J. Koster, R. O. Nelson, M. E. Schillaci, M. Blann, D. Krofcheck, L.Hansen, P. Pohl, V. R. Brown, H. Nifenecker, J. A. Pinston, and D. M. Skopik

Neutron-proton bremsstrahlung is an inelastic processthat involves the emission of a gamma ray following aneutron-proton collision. Both proton-protonbremsstrahlung (PPB) and neutron-proton bremsstrahlung(NPB) probe off-shell regions of the nucleon-nucleoninteraction, but there are significant differences betweenthem. PPB does not allow El radiation, and thecontribution from meson exchange is very small. Thecontribution from meson exchange in NPB has beencalculated to be large and the radiation field ispredominantly electric dipole.

Knowledge of the NPB cross section is important inthe study of the NN interaction because it yieldsinformation about meson-exchange currents. Also, thecross section for this fundamental process is needed tobegin to understand the origin of high-energy gamma raysthat are observed in heavy-ion collisions.

An experiment to measure the NPB cross section overan incident neutron energy range of 50 to 400 MeV hasbegun, using the white neutron source at the WNR targetarea. The target consist of 0.75 f. of liquid hydrogen,located on the 15°-Right flight path, at a distance of 18 mfrom the neutron-production target. We have constructed adetector system, shown in Fig. 1. This detector isefficient for high-energy gamma rays and is relativelyinsensitive to neutrons. It consists of a BaF2 activeradiator, a 3-mm thick plastic detector and a 1-cm thickCerenkov detector for particle identification, and a 40-cm-thick Nal calorimeter. In the first part of the experiment,two such detectors are located at ±90° relative to theneutron beam, and the gamma-ray yield from the NPBreaction is measured as a function of incident neutronenergy.

-BaF2 Radiator

Plastic AE

Nal Calorimeter

-Cerenkov-ChargeParticle Veto

Fig. 1. Neutron-proton bremsstrahlung detector.

During the 1991 run cycle, the liquid hydrogen targetwas assembled, tested, and operated. The detector systemwas fabricated, assembled, and tested. The associatedreadout electronics and the data acquisition code waswritten and used in a short run. The results of this shortrun are presently being analyzed as we develop themachinery to process the data.

During the next run cycle, we shall continue theinclusive gamma production measurement (hat was begunin the last cycle. We shall also assemble a proton detectorsystem and measure proton-gamma coincidences.

70



7Li activation measurements at 795 MeVINSTITUTIONS: Los Alamos National Laboratory, Brookhaven National Laboratory

PARTICIPANTS: John Ullmann (spokesperson), T. N. Taddeucci, A. Ling, and T. E. Ward

The (p.n) reaction on 7Li leading to the ground stateand first excited state (0.43 MeV) in 7Be is a convenientreaction to employ for normalization purposes. Thecombined 0° cross section for (p,n) transitions to thesetwo states is large (>35 mb/sr) and there are no other low-energy-loss 7Li(p,n) channels with appreciable crosssection at 0°; the high-energy flux at this neutronproduction angle is therefore almost monoenergetic.

There are no particle-emission stable states in 7Beabove the first excited state. Residual 7Be nuclei producedby bombarding 7Li with protons must therefore have beenproduced by (p,n) transitions to the ground state or firstexcited state. (It is assumed that alternate productionchannels, such as (p,p'rc~), will contribute negligiblybecause of the large momentum transfer involved.) Thetotal cross section for (p,n) transitions to these two levelscan therefore be measured by counting the number ofresidual radioactive 7Be nuclei. The total cross sectioncan also be obtained, to within an overall normalizationfactor, by integrating the differential-cross-section angulardistribution for the (g.s. + 0.43-MeV) transition. Com-parison of the two results gives the proper normalizationfactor for the differential-cross-section distribution.1

Differential-cross-section distributions have been•neasured for energies up to 800 MeV (Ref. 2). Until thepresent experiment, however, activation data existed onlyfor energies up lo 500 MeV (Ref. 3). Normalization ofthe higher-energy differential cross sections therefore reliedupon an extrapolation of the activation cross sections forenergies above 500 MeV (Ref. 2). We report here new7Li(p,n)7Be activation measurements that extend the rangeof the activation data up to 800 MeV.

In August (99), four 7Li targets were irradiated witha 795-MeV proton beam at the Target-2 area ("BlueRoom") in the Weapons Neutron Research (WNR)

facility. The number of 7Be atoms produced in theirradiations was determined by observing the 478-keVgamma rays following the 10.45% electron capture decaybranch of 7Be. The lithium metal targets were enriched to96.50% in 7Li and were cold-rolled to a uniform thicknessof either 1 mm or 2 mm (55 mg/cm2 and 110 mg/cm2).Each target was covered on the front and back by threelayers of aluminum foil (4.2 mg/cm2). Beam integrationwas accomplished by counting 1368-keV gamma raysfrom the decay of 24Na created in the two center Al foilsby the 27Al(p,3pn)24Na reaction.4

Beam intensities varied from 180 nA to 450 nA andirradiation times varied from 155 s to 1220 s. Initialactivities in the Al foils ranged from 8 - 7 5 kBq and weremonitored for approximately six half-lives (t|/2 = 15 h).Initial activities in the 7Be targets ranged from 0.35 -1.45 kBq and were monitored for about 0.35 half-lives(t)/2 = 53.3 d). All of the targets were counted in astandard geometry with a HPGE detector. A calibratedgamma-ray reference source was used to establish both theenergy scale and the efficiency of the detector.

The 7Li(p,n)7Be(g.s. + 0.43-MeV) total cross sectionderived from each of the lithium targets is plotted inFig. 1. The horizontal lines in this figure representextrapolated values based on two different parameteri-zations of the previous lower-energy dala.2 Agreementwith the new data is good.

The average value of the four data points in Fig. I isG J O T = 0.62 ± 0.02 mb. The uncertainty includesrandom contributions from counting statistics (Li and Al),target thickness (4.3%) and peak fitting (<l%), andsystematic contributions from detector efficiency (0.89c).half life (0.13%), branching ratio (0.38%), and 2 4 N across-section normalization (2.2%). Figure 2 shows thenew result plotted with previous lower-energy da ta.

71


Fig. I. Total cross section for the Li(p,nyBe(g.s. +0.43-MeV) reaction at 795 MeV derived from activationmeasurements on four different targets. The horizontallines represent extrapolations from previous lower-energydata (Ref. 2).

References

1. S. D. Schery. L. E. Young, R. R. Doering, S. M.Austin, and R. K. Bhowmik. Nucl. lustrum. Methods147. 399 (1977).

Bombarding Energy Ep (MeV)

Fig. 2. Activation total cross section for theLi(p,n) Be(g.s. + 0.43-MeV) reaction as a function of

bombarding energy.

2. T. N. Taddeucci, W. P. Alford, M. Barlett, R. C.Byrd, T. A. Carey et al., Phys. Rev. C41, 2548(1990).

3. J. D-Auria, M. Dombsky, L. Moritz, T. Ruth, G.Sheffer e'. al., Phys. Rev. C30, 1999 (1984).

4. J. B. Cumming, V. Agoritsas, and R. Witkover,Nucl. lustrum. Methods 180, 37 (1981).



Studies of Gamow-Teller and giant resonance excitation inthe (n,p) reaction at the WNRINSTITUTIONS: Los Alamos National Laboratory, Ohio Univ., Univ. of California at Davis, Duke Univ.

PARTICIPANTS: J. L. Ullmann (spokesperson), J. Rapaport (spokesperson), R. C. Haight (spokesperson), D. S.Sorenson, A. G. Long, P. W. Lisowski, B. K. Park, X. Yang, L. Wang, J. L. Romero, F. P. Brady, C. R.Howell, and W. Tornow

In nuclei with a neutron excess, the (n,p) reactionprovides information on nuclear structure that isfundamentally different from that measured in the (p,n)reaction. The WNR "Target 4" White Neutron source onLine D provides an intense continuum of medium-energyneutrons, and an experiment to measure the (n,p) reactionat energies from 50 to 250 MeV has been under way. Thisexperiment uses a "wall" of Csl detectors to measure theproton energy. The neutron energy maps out the regionof rapid change in the vst/vt ratio, and therefore provides atool for studying spin versus nonspin excitations.

The first stage of the experimental program concen-trated on Gamow-Teller strength in light nuclei. Theseexperiments provided a "calibration" of cross section vs.measured beta-decay B(GT) strengths.' Of particular inter-est was the first measurement of this ratio for the (n,p)reaction in the fp-shell, using the ^Ni(n,p) reaction.^

The second stage involved studying giant resonancesand Gamow-Teller strength in heavier self-conjugatenuclei, 3 2 S and 4 0Ca. Figure 1 shows the 4 0Ca(n,p)response surface at 7° in the lab.^ The giant dipoleresonance (GDR) is obvious as a single bump at 12.5-MeV excitation at 60 MeV. At the highest beam energy,it has been replaced by a broader structure identified as thegiant spin-dipole resonance (GSDR).

A detailed multipole analysis of the spectra was madeover the angle range 0° to 40° (Ref. 3). The Gamow-Teller strength for two states at 2.7 and 4.3 MeV wasfound to be 0.14 ± 0.02 and 0.17 ± 0.02, in subsiantialagreement with (p,n) measurements.4 The total GTstrength up to 15 MeV was found to be B(GT) = 1.6 +0.1. The very existence of GT strength in spin-saturatednuclei like 4( 'Ca is taken to be evidence for ground-state

correlations. Recent calculations for 4 0 Ca predict GTstrength of the same order of magnitude as measured inthis experiment, but are quite sensitive to the interactionthat was used.-*

The multipole analysis at 170 MeV also determinedL = I strength, presumably giant spin-dipole, up to35 MeV in excitation. This strength is only about 20%that predicted from naive lp-lh shell-model calculations,and extends to higher excitations than predicted. It isanticipated that more sophisticated calculations that alsoinclude ground-state correlations would be in betteragreement with our measurements.

References

1. D. S. Sorenson, J. L. Ullmann, A. G. Ling, P. W.Lisowski, N. S. P. King, R. C. Haight et al., Phys.Rev. C (March 1992).

2. A. G. Ling, X. Aslanoglou, F. P. Brady, R. W.Finlay, R. C. Haight, C. R. Howell et al.. Phys.Rev. C44 , 2794 (1991).

3. B. K. Park. "Energy Dependence of Gamow-Tellerand Dipole Strength Distribution in A = 32 and A =40 Nuclei via (n.p) Reactions." Ph.D. thesis, OhioUniversity (1991); B. K. Park, J. Rapaport. J. L.Ullmann. A. G. Ling. D. S. Sorenson. F. P. Brady etal.. Phys. Rev. C 45, 1791 (1992).

4. T. N. Taddeucci. J. Rapaport, C. C. Foster. C. D.Goodman, C. Gaarde. J. Larsen et al., Phys. Rev.C 2 8 . 2511 (1983).

5. S. Adachi. E. Lipparini, and N. Van Giai. Nucl.Pins. A MS. 1 (1985).

7 3


Fig. 1. The ™Ca(n,p) response surface at 7°. The neutron beam energy is shown along the right axis and excitation energyalong the left axis. The giant dipole (GDR) and giant spin dipole (CSDR) are indicated.

74

Researchflstrophysics

Astrophysics

CYGNUS experimentINSTITUTIONS: Los Alamos National Laboratory, Argonne National Laboratory, UC Irvine, UC Riverside, UC Santa Cruz,

Univ. of Maryland, George Mason Univ., Univ. of Notre Dame

PARTICIPANTS: R. L. Burman, C. M. Hoffman (spokesperson), D. E. Nagle, M. E. Potter, V. D. Sandberg, C. Sinnis, S.Stanislaus, W. Zhang, S. Freedman, B. Fujikawa, D. A. Krakauer. D. E. Alexandreas, S. Biller, R. S.DeLay, G. M. Dion, X-Q. Lu, A. Shoup, P. R. Vishwanath, G. B. Yodh (spokesperson), J.-P. Wu, M.Cavalli-Sforza, D. Coyne, D. Dorfan, L. Kelley, S. Klein, D. A. Williams, D. Berley, C. Y. Chang, B. L.Dingus, C. Dion, J. A. Goodman (spokesperson), T. J. Haines, P. Kwok, M. Stark, R. W. Ellsworth, andD. R. Cady

The CYGNUS detector at LAMPF is an extensiveair-shower array that detects Ultra High Energy (UHE.50 TeV - 10 PeV) cosmic gamma rays. The purpose isto search for discrete sources of UHE gamma rays (such asneutron stars and black holes), to understand themechanism of the cosmic accelerators within thesesources, and to study the interactions of the UHE gammarays in the earth's atmosphere. The CYGNUS detectorconsists of 204 scintillation counters, each with an area of-0.85 m-, deployed around the LAMPF beam stop,covering an area of ~8 x 10* m-. Several shieldeddetectors, including the MWPCs from the neutrinodetector formerly used in LAMPF Exp. 225. and thescintillator shield formerly used in Exp. 645, are used tomeasure the muon content of the showers. Theexperiment started operation in 1986, albeit with a smallernumber of detectors at the beginning, and has been incontinuous operation since. The university collaboratorsare funded by the NSF and DOE. while the Los Alamoscomponent has bi.-n funded by Laboratory DirectedResearch and Development (LDRD) funds.

Past observations have established that the compactx-ray sources Cygnus X-3 and Hercules X-l are sources ofUHE gamma rays. The observations, the most compellingof which was published by the CYGNUS Collaboration,show that the gamma-ray interactions in the atmosphereproduce far more muons than expected. Either the natureof photon interactions changes dramatically at theseextremely high energies, or the primary particle is some

hitherto unknown light, neutral particle; either of thesepossibilities indicates exciting, new physics.

An extensive data set, spanning the years 1986-1991.is being intensively analyzed. We have searched for steadyemission from anywhere in the northern sky and from anumber of potential UHE sources, including x-raybinaries, isolated pulsars, cataclysmic variables, and otherintense x-ray sources. We see no evidence for steadyemission from any of these sources; Table I, from a recentpublication in Astrophysical Journal, gives the 90%confidence level upper limits on the integral fluxes above40 TeV from these objects. We are preparing papers ondaily emission from these sources and detailed analyses onemission from Hercules X-l. the Crab, and 4U0115+63.

The CYGNUS group has installed five waterCerenkov detectors within the existing array. Thesedetectors are actually above-ground swimming pools eachwith seven 10" photomultiplier lubes (PMTs).Calculations indicate that these detectors shouldsignificantly improve the angular resolution of CYGNUS.perhaps by as much as a factor of two. This wouldgreatly enhance our ability to distinguish signals frompoint sources over the isotropie background. The poolswere installed during the summer of 1991 and the datafrom them are recorded as part of the CYGNUS datastream. Figure 1 gives the time response of the PMTs ina pool relative to the shower front as reconstructed by thescintillation counters. The narrow width of thisdistribution (o = 1.8 ns) agrees with expectations based onMonte Carlo simulations.


Table I. The limits from 49 potential point sources. No n and Non are the number of events observed from the sourceposition and the number expected from the cosmic-ray background. N o is the number of standard deviations excess above thebackground. F[jnl is the 90% confidence-level upper limit on the fractional excess above the background, and the flux limit.F(). is assuming a differential power law spectral index of-2.7.

Source

Cyg X-3

HerX- l

Crab

CygX-lM31Virgo AAM HerDQ HerU GemSS CygniHZ 43GKPerV404 CygniKiel 1Kiel 3Kiel 4Kiel 5Kiel 6Geminga1E2259+58SS4334UOO42+324U0115+634U0316+414U0352+304U0614+094U1257+284U1651+394U1837+044U1901+034U1907+094UI918+I541'1957+404U1954+314U2142+384U232I+582CGO65+OO2CGO75+OO2CG078+002CG095+042CG135+01

a

n

307.7254.082.9

299.19.9

186.9273.7271.6118.0325.2198.552.0

300.436.0

270.336.2

352.73.4

97.4344.8287.3

10.518.849.158.193.6

194.4252.9279.4285.4286.8289.7299.3298.5325.6350.3298.7304.8305.4318.8

38.2

5

40.835.422.035.141.012.749.845.922.143.429.443.733.832.342.661. J67.425.917.858.6

4.9

32.863.541.430.99.2

28.239.95.0

3.1

9.7

15.040.532.038.158.628.736.439.855.061.7

N()n

9486995774647929630885459

43114861848974765949924668564184677902097989493139488343351471023566735749925457

8088743296837567961232400848929761925899

21316

37507

50851

967259(H)4991096569888790894480969706670846680

Non-

9485995956643259644185417

42801866889022866038925748617884351901347972192784492383349070593563395771825413806834305183821

7936632273847029726825831214493718051124963339021 390358571028807595241967956720146803

Na

0.0

-0.61.8

-0.40.1

1.5

-1.7-1.6-0.4-0.4-1.8

I.I

0.20.6

1.2

-1.80.1

1.6

1.4

-0.90.3

0.7

1.2

-0.20.9

0.7

0.6

i.l0.4

-0.91.7

— I ̂

1.3-0.6

2.4

-0.5-0.6-2.5

0.6

-1.9-0.6

•""limC/r ofCRs)

0.570.471.280.480.631.420.340.350.600.510.340.900.630.760.850.451.011.151.200.541.220.791.280.550.851.250.760.831.280.891.610.5 i0.870.481.280.630.490.260.690.370.67

F0O40TeV)(xlO-^cm-V',

1.9

1.6

4.4

1.6

2.24.8

1.2

1.2

2.1

1.71.0

3.0

2.1

2.6

2.0

1.5

3.43.9

4.1

1.8

4.1

2.7

4.3

1.9

2.9

4.3

2.6

2.84.3

3.0

5.4

1.7

3.0

1.6

4.4

2.1

1.7

0.9

1.22.3

7 6

Research

Table 1 (continued).

Sourcea 5

NOn Noff fFlim

<ia (VrofCRs)

Rstrophysics

F()(>40TeV)

2CG212+04PSR0355+54PSR0950+08PSR1929+10PSR1937+21PSR1951+32PSR1953+29PSR1957+20

7.258.8

147.6292.5294.4297.8298.2299.4

66.554.18.2

10.921.532.729.220.7

3572065304308744017371285898898842669072

3563564833311144030171167903778862069234

0.41.8

-1.4-0.6

0.4-1.6-0.6-0.6

1.091.280.620.700.770.350.470.53

3.74.32.12.42.6

1.2

1.6

1.8

Fig. I. Time response of the PMTs in a pool at a radius 20-i() in from the shower core relative to the shower (rout asreconstructed In the scintillation counters.


Publications and Papers

D. E. Alexandreas, D. Berley, S. D. Biller. R. L. Burman,D. R. Cady, C. Y. Chang et al.. "A Search of theNorthern Sky lor Ultra High Energy Point Sources,"Asuophys. J. Lett. 383 , L53 (1991).

D. E. Alexandreas, R. C. Alien. S. D. Biller, R. S.Delay. G. M. Dion. X-Q. Lu et al., "The CYGNUSExtensive Air-Shower Experiment," Nucl. lustrum.Methods A 311, 350(1992).

R. C. Allen, R. L. Burman, D. R. Cady. C. Y. Chang,R. S. Delay. R. W. Ilsworth el al., "Use of a NeutrinoDetector for Muon Identification by the CYGNUS Air-Shower Array," Nucl. lustrum. Methods A 311, 368(1992).

D. E. Aiexandreas, G. Allen, D. Berley, S. D. Biller, R.L. Burman, D. R. Cady et al., "Search for Daily Emissionof Ultra High Energy Radiation from Point Sources," LosAlamos National Laboratory document LA-UR-92-2082(submitted to Aslrophyskal Journal Letters. 1992).

D. E. Alexandreas, S. D. Biller, G. M. Dion, J. A.Goodman, T. J. Haines. C. M. Hoffman et al., "PointSource Search Techniques in Ultra High Energy GammaRays," Los Alamos National Laboratory documentLA-UR-92-1546 (submitted to Astrophysical Journal,1992).

D. E. Alexandreas, D. Berley, S. D. Biller, R. L. Burman,D. R. Cady, C. Y. Chang et al., "Search for DailyEmission of Ultra High Energy Showers from PointSources with the CYGNUS Experiment," in 22ndInternational Cosmic Ray Conference, Dublin, Ireland,August 11-23, 1991 (Reprint. Ltd., Dublin, Ireland),Vol. 1. p. 301.

D. E. Alexandreas, D. Berley. S. D. Biller. R. L. Burman,D. R. Cady. C. Y. Chang et al., "Detailed Simulation ofthe CYGNUS Array's Response to Extensive AirShowers." in 22nd International Cosmic Ray Conference,Dublin, Ireland, August 11-23, 1991 (Reprint, Ltd.,Dublin. Ireland), Vol. 4. p. 504.

D. E. Alexandreas. D. Beriey, S. D. Biller, R. L. Burman.D. R. Cady, C. Y. Chang et al.. "Characteristics of'Anomalous Muon' Events Associated with HerculesX-l." in 22nd International Cosmic Ray Conference,Dublin, Ireland, August 11-23. 1991 (Reprint. Ltd..Dublin, Ireland), Vol. I, p. 249.

D. E. Alexandreas, D. Berley, S. D. Biller, R. L. Burman.D. R. Cady. C. Y. Chang et al., "A Search for SteadyEmission from Ultra High Energy Sources," in 22ndInternational Cosmic Rax Conference, Dublin, Ireland.August 11-23, 1991 (Reprint, Ltd., Dublin, Ireland),Vol. 1, p. 436.

D. E. Alexandreas, D. Berley. S. D. Biller, R. L. Burman,D. R. Cady, C. Y. Chang et al., "Angular Resolution ofthe CYGNUS EAS Array from the Shadows of the Moonand Sun," in 22nd International Cosmic Ray Conference,Dublin, Ireland, August 11-23, 1991 (Reprint, Ltd..Dublin, Ireland), Vol. 2, p. 672.

D. E. Alexandreas, D. Berley, S. D. Biller. R. L. Burman.D. R. Cady, C. Y. Chang et al., "Search for UHE CosmicRays from the Crab Nebula/Pulsar," in 22nd InternationalCosmic Ray Conference, Dublin, Ireland, August 11-23,1991 (Reprint, Ltd., Dublin, Ireland). Vol. 1, p. 216.

D. E. Alexandreas, D. Berley, S. D. Biller, R. L. Burman.D. R. Cady, C. / Chang et al., "Search for Pulsed UHEEmission from 4U0115+63," in 22nd InternationalCosmic Ray Conference, Dublin, Ireland, August 11-23.1991 (Reprint, Ltd., Dublin, Ireland), Vol. 1, p. 352.

D. Berley, C. L. Dion, J. A. Goodman, T. J. Haines, P.W. Kwok. M. J. Stark et al., "JASA, Initial Results froma Prototype Water-Cerenkov Air-Shower Detector," in22nd International Cosmic Ray Conference. Dublin.Ireland. August 11-23, 1991 (Reprint, Ltd., Dublin.Ireland), Vol. 2, p. 680.

D. E. Alexandreas, D. Berley, S. D. Biller. R. L. Burman.D. R. Cady, M. Cavalli-Sforza et al., "Studies onImproving the Angular Resolution of the CYGNUSArray." in 22nd International Cosmic Ray Conference,Dublin. Ireland, August 11-23. 1991 (Reprint, Ltd..Dublin. Ireland), Vol. 2, p. 676.

78

ResearchRtomic and Molecular Physics

Atomic and Molecular Physics

EXPERIMENTS 1121 AND 1127 - HIRAB

Relativistic H~ spectroscopyINSTITUTIONS: Univ. of New Mexico, Los Alamos National Laboratory, Hungarian Academy of Sciences (Hungary), City

College of New York, Univ. of Connecticut, Hunter College, TMA/Eberline Analytical Laboratory

PARTICIPANTS: H. C. Bryant (spokesperson, Exp. 1121, 1127), W. Becker, Janos Bergou, K. B. Butterfield, S. Cohen,L. A. Collins, J. B. Donahue (spokesperson, Exp. 1121), J. R. Friedman, M. Halka, P. G. Harris, A. Hsu,Peter Kalman, G. A. Kyrala, K. LaGattuta, M. Lubell, E. P. MacKerrow, W. Miller, A. H. Mohagheghi,C. R. Quick (spokesperson, Exp. 1127), R. A. feeder, K. Rozsa, W. W. Smith, C. Y. Tang, J. J. Tiee',and O. B. van Dyck

Work at the High Resolution Atomic Beam Facility(HIRAB) continues on the spectroscopy of the H~ systemusing relativistic beams crossed with pulsed lasers.PrincipaJ advances in the past year have concernedmultiphoton detachment of H~, multiphoton absorptionin H°, and the study of single photon detachment inelectric fields. In addition, we have commenced studies onthe design of a collimator system, which would limit theH~ current delivered to HIRAB in the event of a worst-case accident.1

Multiphoton Detachment

Figure 1 displays recently published data on themultiphoton detachment of electrons from H~. These datawere acquired using a Doppler-shifted infrared laser beamfrom a CCb laser (X = 10.6(i) operated in the TEMootransverse mode and single longitudinal mode, linearlypolarized. The H~~ ions were subjected to bursts of laserlight of approximately 240 femtosecond duration (thetransit time of the particles through the laser focus) atpeak intensities ranging up to 12 GW/cm2 in thelaboratory frame. The actual intensities in the H~ framevaried with the angle of intersection of the two beamsaccording to the formula

hvc.m. = Yd + P cos (2)

•cm. = Y2( I + P cos a ) 2 I | a b . (1)

where y = 1.853 and P = 0.842 for the 800-MeV H~beam.

Since the variation of the laser photon energy is

the ponderomotive energy, which goes like the intensityover the frequency squared, is invariant. Therefore, each ofthe curves in Fig. ! is for a constant ponderomotiveenergy: 120, 60, and 40 meV for (a), (b), and (c),respectively. These data are significant because we areable to scan over transitions from one photon multiplicityto another. Intensity dependent threshold shifts areobserved.

With the new CCb laser system we were able toimprove our data acquisition rate by factor of 20. Thisnew multiphoton data is cunently being analyzed, and wenow have results on multiphoton ionization for differentpolarization states of the laser. Multiphoton absorptionin neutral hydrogen atoms was also observed, and is beingcompared with the multiphoton absorption data for H~.We hope that the different atomic potentials between thesetwo species will shed light on the interaction of stronglasers (I > 1012 W/cm2) with atoms, a process that is notwell understood.

H Photodetachment in Electric Fields

Recent analysis of data from a 1989 HIRABexperiment in which static electric fields were applied tothe H~ photodetachment interaction region highlights newfield-induced structure and threshold shifts. Relativepartial cross sections were measured by detection ofH°(N = 4). H°(N = 5). and H°(N = 6) resulting from laserinteraction with relativistic H" ions. The downward shifts

ResearchHtomic and Molecular Physics

co

oCD

coo

JO)LU

l O 1 ^ -

11c 10

(0GC i o 1 0

10

108

107

106

i i r \ i r i \ i r

t2 z

i i i i i i i i i i i I I i

0.10 0.15 0.20 0.25 0.30

Photon Energy (eV)0.35 0.40

Fig. 1. Intensity-averaged electron detachment rates showing the dependence of the muliiphoton detachment yield from Hversus photon energy for (a) lpeak ~ 12 GW/cm-. (b) lpeak = 6 GW/cm?, and (c) Ipeak = 4 GW/cm^. The arrows indicatethe nominal photon energy required for the onset of N-photon absorption.

in the onset of production increase as the field is increased,and agree with the recent interpretation of Zhou andLin-—work stimulated by these experimental results.Prior to this analysis, no theoretical work had beenundertaken in this area. A new resonance is observed inthe H°(N = 4) threshold region at 13.513 ± 0.001 eV.which may be a field-induced shape resonance. Fieldquenching of the H~ doubly excited resonances was alsoobserved.

The Hf)(4) partial cross-section measurement wasperformed in barycentric field strengths F off). 13. 25. 38.63. and 87 kV/cm. The data in Fig. 2 are from 0, 38. and87 kV/cm runs—sufficient to show the trend withincreasing electric field. Most notable is the large shift of

the threshold toward lower energies. The H('(5) and H°<6)data display similar behavior.

Figure 3 plots the amplitude of the threshold shift AErelative to the zero-field threshold (ZFT) for each fieldstrength. These shifts are nearly an order of magnitudelarger than those expected from Stark splitting of the H°levels, as shown by the dashed lines. The solid lines arefits to a function that is proportional to F-'-\ The shiftshould have this dependence if it results from field-lowering of the potential barrier seen by the outerelectron, so that classically

• = , la1/? P2/3 (3)

80


3000

2000

1000

_ F = 0 kV / cm

0 -

3•

Co

(a) I

+-H—I—I i I I I I I I I I - I -

3000

2000

oa>(/) 1000tn(0O

o -

F = 38 kV / cm

. f* *

I I I [ I I I I I I I I I I I

3000

2000

1000

0

- F = 87 kV / cm

• ' , ' '

/

"it

1 ' , , 1 1 1 , 1 1 1 1 1 ! 1 1

(c) -

-

-

113.40 13.45 13.50 13.55

Photon Energy (eV)13.60

Fig. 2. H^(N - 4) relative partial cross section versus photon energ\ 'tear the N = 4 threshold for three different fieldstrengths. Error bars arc statistical only. Note the sizable drop in threshold energy with increasing field strength.

SI


*

•

CO9o111

O.KJ

2.5

2.0

1.5

1.0

0.5

0.0

I t ! ' | i I t j f I I • [1 1 1

Stark shift x 8*r- r>,n 1/3 r2/3

— i i c — old. a r

I O Zhou and Lin [Ref.1]x This experiment *'

-. \ ^

1 ^ ^- Y^''

SX''''/ '

/ s ** , • • ' 1 1 • 1 i ' • >

' ' i \ 1 1 1 ! | ' • ! ! [

! ! \

(a) ]

• * \ \

-

-

-

-

—

-

(A

o3.0

g 2.5

2.0

1.5

1.0

0.5

f- •irk shift x 6AE = 3/2 a1/3 F273

O Zhou and Lin [Ref.1]x This experiment

(b)

0.0 0.5 1.0

Field (105 a.u.)

1.5

Fig. 3. Threshold shift AE relative to the zero-field threshold versus field strength. Solid line is a fit to the functionAE=(3/2) la I i/j r~2/i " ' " ' ' ' ' " ' dipole moment a as a parameter. Open circles indicate values from calculations of Zhou andLin.- (a) H°f4) threshold shift values. Fit gives a = 11.04 ± 0.19 a.u. Dashed line shows that the shifts are eight timeslarger than those expected from the first-order Stark effect in tfi. (b) Ff{5) threshold shift values. Fit gives a =13.03 ±0.17a.u. Dashed line shows that the shifts are six times larger than those expected from the first-order Stark effect in H*K

82

Research

where a is the dipole parameter of the relevantphotodetachment channel. Our fits using the MINUIT codeprovide | a | = 11.04 ± 0.19 (13.03 ±0.17) a.u. for theN = 4 (5) threshold. These values of a are not consistentwith theoretical dipole moments calculated for the lowest"+" channel in each N-manifold: a4 = -18.5, as = -37.8[from Eq. (9) of Ref. 3]. As explained by Zhou and Lin2,it is found that field-assisted coupling between the "+" and"-" channels plays a significant role here, and the classicalestimate is not adequate. Their values for AE fromquantum mechanical calculations are plotted as opencircles in Fig. 3.

New structure observed in the threshold region maybe partly attributable to field-assisted tunneling of H~(n)doubly excited autoionizing resonances that converge frombelow to each H°(n) threshold. In zero-field these can beobserved only in the H^(N < n - 1) channels because theinner electron must exchange energy with the outerelectron if autodetachment is to occur. However, assuggested by Lin,' an external field may supply the neededenergy to the outer electron, allowing autodetachmentwithout the participation of the inner electron. It wouldtherefore remain in the n level, and be observable in theH°(n) channel. Order-of-magnitude calculations show thatfields used in this experiment are of sufficient strength forthis process to occur, but detailed theoretical work has notbeen carried out.

A particularly intriguing change in the H°(N = 4)cross section appears in F = 87 kV/cm. Figure 2(c)shows that a dip develops, which is not seen in lower fieldstrengths. A fit to the Fano function4 places this featureat 13.513 ± 0.001 eV to 10 meV higher in energy thanthe ZFT. It has been suggested2 that a "+" potential thatmamicsts itself as a Feshbach-type resonance in zero-fieldcan change to a centrifugal barrier when a field is applied,giving rise to a shape resonance above the ZFT. Cross-section calculations prove too computer-intensive, but theenergy of the observed resonance compares favorably withthat calculated by Zhou and Lin using the Wentzel-Kramers-Brillouin (WKB) approximation.

Collimator System

A serious radiation safety issue arose in 1991 over thepossible delivery of high-intensity H~ beam down Line X.If the H~ chopper and the Line D kicker were to fail

Rtomic and Molecular Physics

simultaneously, the high-intensity H~ beam would bedelivered to experimental areas that are inadequatelyshielded for these high currents. This "worst-case"accident has the possibility of inducing radiation levels of104 R/hr/mA from neutron skyshine. The experimentalareas affected are the Medium Resolution Spectrometer(MRS), HIRAB, and the Neutron Time-of-Flight (NTOF)facility. HIRAB received no beam during 1991 due to thispotential danger.

Improved shielding of the NTOF swinger cave hasbeen planned to insure safety for the NTOF area. Ashielding improvement for MRS and HIRAB is difficult.One solution for MRS and HIRAB is to install anacceptance-limiting collimator system between theLine B/Line EP junction and the EPBM-03 bendingmagnet. The collimator system would only accept the P~beam that passes the LBST01 stripper. In the event of theaccident, the LBST01 stripper will fail, and the entire H~beam will be incident on the collimators. The design ofthese collimators is such that the transmitted beam currentto MRS and HIRAB will be approximately reduced by afactor of 100. If the high-intensity H~ is incident on thecollimators, they will burn through and let the beamvacuum up to air pressure. This will put a time limit onhow long the "accident-beam" will last.

Preliminary designs have been made on the collimatorsystem, and a trial run in 1992 is expected to test thefeasibility of beam steering through this low-acceptancesystem. Beam optics in Line B and Line EP are beingdesigned to improve acceptance of P~ while at the sametime reducing acceptance for the high-intensity H".

References

1. Principal investigators: E. P. MacKerrow and O. B.van Dyck.

2. Bin Zhou and C. D. Lin, "Shifts of PhotodetachmentThresholds of H~ in an Electric Field" (submitted toPhysical Review Letters by Kansas State University,1992).

3. H. R. Sadeghpour, Phys. Rev. A 43, 5821 (1991).4. U. Fano, Phys. Rev. 124, 1866 (1961).

C. D. Lin. private communication. Manhattan, Kansas,1991.

ResearchMaterials Science

Materials Science

EXPERIMENT 1235

Muon level-crossing resonance spectroscopyINSTITUTIONS: Los Alamos National Laboratory, San Jose State Univ., TRIUMF, Rutherford Appleton Laboratory (UK),

Leicester Univ., Rice Univ., Texas Tech Univ., California State Univ. at San Luis Obispo, Univ. ofCincinnati

SPOKESMEN: D. W. Cooke (spokesperson), M. Leon (spokesperson), M. A. Paciotti (spokesperson), C. Boekema, J.Brewer, S. Cox, E. Davis, T. Estle, B. Hitti, R. Kiefl, J. Lam, D. Lamp, R. Lichti, A. Morrobel-Sosa, J.Oostens, and J. Schneider

Muon Level-Crossing Resonance (U.LCR) spectros-copy is a variant of the Muon Spin Rotation/Relaxation(U.SR) method in which a cross relaxation occurs. Instandard time-differential u_SR, polarized muons areimplanted in a sample one at a time, and tht timeevolution of the muon polarization is measured bydetecting the emitted positrons. The muon decays with a2.2-|is lifetime, with the daughter positron emittedpreferentially in the spin direction, so that the timeevolution of the muon polarization can be followed. In atransverse magnetic field, the spin of the muon precessesand one measures the time distribution of the emittedpositrons,

N(<|>,1) = No exp(-t/xu) [I + aGx(t) cos(wut + if)] + B. (1)

Here a is the asymmetry and Gx(t) is the relaxationfunction, typically Gaussian or Lorentzian, dependingupon the distribution of local magnetic fields. Thetechnique provides information on these local magneticfields and has been widely applied. Making the correctcorrelation between the entry of a muon and detection of apositron requires that only a single muon enter the sampleduring an ~20-|is interval. This requirement limits thedata rate at CW accelerators; at LAMPF, the data rate isfurther reduced by the duty factor.

A rather different |iSR method was suggested byAbragam in 1984.1 This technique, |iLCR, involvesscanning a longitudinal magnetic field to find those valuesfor which resonant transfer of muon polarization toneighboring nuclei takes place. This will occur when themuon Zeeman splitting is degenerate with the energysplittings of the neighboring nuclei. This energy

splitting can come from nuclear quadrupole plus Zeemaninteraction; in some cases, the hyperfine interaction withan unpaired electron is also involved. Valuableinformation about the interactions of the nearby nuclei canbe obtained from |iLCR, which complements theinformation about the interactions of the muon providedby standard |aSR.

An important feature of (J.LCR is that it can be donein an integral mode instead of the more usual time-differential mode. Hence, the limitations on data rate andthe LAMPF duty-factor handicap are both removed. Whatis measured is the net forward-backward asymmetry,

(2)

where Gz(t) is the longitudinal relaxation function. Asthe field is scanned through resonance, A will show asmall dip (typically <2%).

However, the integral mode has a disadvantage thatdoes not show up in time-differential (iSR: A isespecially susceptible to drifts in the ratio Np/Ng that canoverwhelm the signal. To avoid this problem,experimenters at TRIUMF and RAL commonly usesupplementary coils that generate an incremental magneticfield of alternating sign, in addition to the main scanningfield. By taking the difference in A over many "fieldflips," the effect of drifts is significantly reduced.

A surface muon beam (28 MeV/c) was developed atthe Stopped Muon Channel (SMC) with spot size 4 cm x1.5 cm (FWHM), high asymmetry and flux, and goodstability. The calibration curve of Fig. 1 shows the ratioof counts in the downstream and side positron counters asa function of transverse magnetic field; the variation

84

Research

1 RI .O

1.5

1.4

1.3

1.2

1.1

1.0

AP

" e =

Run 106 Hanle Scan

= 0.33 6 I190 i f

\ n

i i T I I

-60 -40 -20 0 20 40

Magnetic Field (Gauss)60

Fig. 1. Plot of counter ratio F/S (front/side) as a functionof transverse field, with fitted curve.

Materials Science

(F/S-<F/S>),'Cf/s(0.75 Hz)

18.6

12.4

6.2

l >

-6.2

-12.4

-18.6

20 40 60 80 100 120

Bin Number (Field, H)

Fig. 2. Variation of F/S over 3600 scans.

corresponds to an asymmetry of 0.33. After initial cutswere made to eliminate the data from interruptedbeam,short macropulses, etc., the ratios of e+ detectorcounts were found to be remarkably free of systematicdrifts. Figure 2 shows the results obtained by simulatingthe ramping over a magnetic field interval many times(40 min. x 45 cpm). The deviation of the ratio from itsaverage value is plotted in units of the expected statisticalstandard deviation (6 x 10~4); no variation outside of thatexpected from counting statistics alone is observed. Itappears, therefore, that this kind of averaging is adequatefor detecting a small dip in asymmetry as a function offield; in contrast to TRIUMF and RAL, no "flip field" andsubtraction will be required at LAMPF.

Culminating our beam development and testing was ameasurement of the (iLCR signal in single-crystal copperat 50K. The results displayed in Fig. 3 show a resonanceat 80 Oe, in agreement with previous measurements.2

These studies have convinced us that the combinationof high rate (~2 x 107 \i+/s average) and beam stabilitymake the LAMPF SMC an excellent place to dospectroscopy.

CO

u.

.885

.875

.865

.855

I I

_ /

I I40 60 80

Magnetic

I !

\ :

I ^ ^100 120 140

Field (Oe)

Fig. 3. fiLCR resonance in single-crystal Cu at 50K.

References

I. A. Abragam, Complex Rendus Acad. Sci. Paris 229,85(1984).

2. S. R. Kreitzman. J. H. Brewer, D. R. Harshman, R.Keitel, D-Ll. Williams, K. M. Crowe, and E. J.Ansaldo. Pins. Rev. Lett. 56, 181 (1986).

ResearchRadiation Effects

Radiation Effects

Radiation damage and radiation effects to materials

W. F. Sommer (Los Alamos)

Spectral Correlation Studies

The neutron spectrum at the Los Alamos SpallationRadiation Effects Facility (LASREF) contains neutronswith energies >20 MeV and up to, in principle, the energyof the incoming proton at 800 MeV. At "fast" fissionreactors the neutron energy is generally less than 5 MeVand peaks in flux at about 1 MeV. A fusion reactorneutron spectrum contains a very large flux at near14 MeV. Radiation damage parameters are dependent onneutron energy and subsequent radiation effects may alsoshow this dependence. There is an ongoing interest indetermining a correlation among these neutron spectra sothat experience with material in one neutron environmentmight be inferred for other neutron environments.

A team from Battelle-Pacific Northwest Laboratories,Kyushu University, and Los Alamos has compared theradiation-induced microstructure in pure copper afterirradiation at LASREF, the 14-MeV neutron source at theRotating Target Neutron Source (RTNS), and the fissionspectrum at Omega West Reactor (OWR). At a lowdamage level, <0.02 displacements per atom, themicrostructures are very similar after exposure to each ofthe three sources.1 The comparison uses the calculateddamage parameter of total atomic displacements as liienormalization among the three sources.

In addition, the tensile strength of pure copper,alumina-dispersion-hardened copper alloy, and AISI alloy316 stainless steel was compared after exposure to each ofthe radiation environments.^ When compared on the basisof calculated displacements per atom, the stainless steeland copper alloy showed very similar radiation-inducedhardening for each of the three sources. The pure coppershowed a different hardening in each of the sources,

although the microstructures were found to be verysimilar.

It is now necessary to extend these measurements tohigher doses. It is possible that the radiation-inducedtransmutation products generated through spallationreactions at LASREF will act as impurities and thus affectmicrostructural evolution in a manner different than in afission and fusion reactor environment. We havemeasured the production of the transmutation producthelium at LASREF^ and found the rate to be 100 timesgreater than in a fission reactor environment and 50%greater than in a fusion reactor environment. It isexpected that these differences in helium production, aswell as differences in solid transmutants, will affectproperty changes at high dose.

Material Testing for Fusion Reactors

A Los Alamos Laboratory Directed Research andDevelopment project was initiated with two goals:

1. Determine the basic physics governing changesin the optical properties of fibers intended for useas data transmission lines in fusion reactordiagnostic components.

2. Determine the neutron flux enhancement andspectrum modification possible at LASREFthrough changes in target material and geometry.This is a three-year program that includescollaborators from University of Missouri-Rolla,Iowa State University, University of Illinois, andLos Alamos MEE, MST, and MP Divisions.

86

Research

Accelerator Transmutation of Waste(ATW) and Accelerator Productionof Tritium (APT)

Experience at LAMPF in material lifetime forcomponents such as the proton beam entry window hasbeen applied to planning for the ATW and APT target andblanket. Plans are also being made to utilize LAMPF asa test bed for materials development, as well asdemonstrations of nuclear and chemical processes;LAMPF is unique in providing high-energy particles insufficient quantity for these studies. In 1991, we testedthe stability of L i x R u 0 4 in the neutron flux atLASREF.4 Ru is a product of neutron capture on Tc, afission product that is to be transmuted in ATW. Thisexperiment begins to determine procedures necessary forcontinuoi'j processing at ATW.

References

1. T. Muroga, H. L. Heinisch, W. F. Sommer, and P.D. Ferguson, "A Comparison of Microstructures inCopper Irradiated with Fission, Fusion, and

Radiation Effects

Spallation Neutrons," presented at the FifthInternational Conference on Fusion ReactorMaterials, Clearwater, Florida, November 17-22.1991 (to be published in the Journal of NuclearMaterials).

2. H. L. Heinisch, M. L. Hamilton. W, F. Sommer,and P. D. Ferguson, "Tensile Property Changes ofMetals Irradiated to Low Doses with Fission, Fusion,and Spallation Neutrons," presented at the FifthInternational Conference on Fusion ReactorMaterials, Clearwater, Florida, November 17-22,1991 (to be published in the Journal of NuclearMaterials).

3. W. F. Sommer, B. M. Oliver, and F. A. Garner,"Helium Production Rates in the LASREF Facility,"Semiannual Progress Report, 1991, DOE/ER-0313/11.

4. M. A. Yates, S. A. Kinkead, A. P. Sattelberger, K.D. Abney, N. C. Schroeder, M. Attrep, and W. F.Sommer, "Speciation and Nuclear Chemistry ofRuthenium OXO Anions in an Intense Broad EnergyNeutron Flux," presented at the American ChemicalSociety 203rd National Meeting, San Francisco,California, Spring 1992.

87

ResearchRadioisotops Production

Radioisotope Production

INC-11 radioisotope production activitiesPARTICIPANTS: R. Baca, A. Herring, R. Lopez, B. Garcia, M. Garcia, J. Garcia, R. Gritzo, V. T. Hamilton, D. Heaton, D.

Jamriska, S. Maestas, L. McCurdy, A. Mitchell, M. Montoya, M. Ott, E. Peterson, D. Phillips, R.Staroski, and W. Taylor

Stable and Radioactive IsotopeProduction and Separation

A significant portion of the Group INC-11Radioisotop1. program involves producing and shippingradioisotopes for the medical research community. These

radioisotopes are generally unavailable commercially orcan be made in high yields only at LAMPF. GroupINC-11 provides these radioisotopes on a cost-recoverybasis to interested researchers. During FY 1991, weshipped isotopes to a total of 54 organizations around theworld and to groups at Los Alamos (see Table I).

Table I. Medical Radioisotope Shipments.

Isotope CustomerNo. of

ShipmentsShipped(mCi)

Received(mCi)

7 2As

7Be

CSNSM, FranceHarwell Laboratory, UKTRIUMF, CanadaUniversity of Manchester, England

University of Texas

EPA/RSOU.S. Geological SurveyUniversity of ArizonaUSDA, Grand Forks, North DakotaWallher-Straub Institute, GermanyWayne State University

Amersham International, UKBatelle/U.S. DOEIsotope Products LaboratoryMcClellan AFBU.S. Department of Energy

0.0063 0.0063

190

22

95.00

22

H8

Table I (continued).

Isotope CustomerNo. of

Shipments

Radioisotope

Shipped(mCi)

ResearchProduction

Received(mCi)

109Cd Batelle/U.S. DOEE. 1. Dupont/NEN ProductsIsotope Products LaboratoryNorth American Scientific

6 7 Cu Brookhaven National LaboratoryCalifornia State UniversityIBM Research CenterLANL/INC-ll

Medical Research Council, UKNational Institutes of HealthOak Ridge National LaboratoryPaul Scherrer InstitutePurdue UniversityTexas A&M UniversityTexas InstrumentsUniversity of California, DavisUniversity of Medicine and Dentistry of

New JerseyWashington University

Computer Technology and ImagingCross Cancer Institute, CanadaDuke UniversityEi. I. Dupont/NEN ProductsE. I. Dupont/Washington UniversityIsotope Products LaboratorySociete Gondrand, FranceTurku University, FinlandUniversity Hospital/Cleveland

Brookhaven National LaboratoryE. I. Dupont/NEN Products

Instituut Stralingsfysika, BelgiumLANL/P-6University of Pittsburgh

Isotope Products Laboratory

8 2Sr E. R. Squibb & Sons

4 8V University of Washington

12 3039 3036

31 1615 1296

17 1095 1091

1645 1477

1

8

1

0.001

9016

4

0.001

8600

4

ResearchRadioisotope Production

Table I (continued).

No. of Shipped ReceivedIsotope Customer Shipmen's (mCi) (mCi)

88Y Amersham International, UK 26 78 77

Analytics, Inc.Bionetics Research, Inc.Brookhaven National LaboratoryE. I. Dupont/NEN ProductsHoechst, GermanyIsotope Products LaboratoryNational Institutes of HealthNational Research Council, CanadaRoyal Institute of Technology, SwedenTeijin, JapanU.S. Bureau of MinesUniversity of California, DavisVA Medical Center

88Zr Vrije Universiteit. The Netherlands 1 2 2

TOTAL 120 16718 15712

ResearchTheory

Theory

Pion-induced elastic and inelastic scattering above the 3,3resonance

PARTICIPANTS: E. Oset (Universidad de Valencia, Spain) and D. Strottman (Los Alamos)

Recently, the study of pion-induced elastic, inelastic,single- and double-charge-exchange reactions1-2 in theenergy regime of 300 to 550 MeV has begun at LAMPF.In addition, there exist data-3 from an experiment at800 MeV/c with which we may compare calculations. IfPILAC is constructed, there will be da*a for such react; ^nsto even higher energies. We have calculated pion elasticand inelastic scattering from several nuclei for pion kineticenergies to 1.2 GeV.

In this work we employ the Glauber model for whichthe only input required is the free JiN phase shifts and ashell-model description of the nuclear wave functions. Ithas the advantage of being microscopic, yet has beenfound to provide reliable estimates of cross sections atresonance energies. Finally, the effects of higher partialwaves may be easily and explicitly included. The wavefunctions for mass twelve were obtained using the matrixelements of Cohen and Kurath.4 The oscillator parameterobtained from electron scattering5 is a 2 = 0.39 fm~2 forI 2 C. This value includes corrections for the proton finitesize. We have varied the oscillator parameter for ' -C toinvestigate whether the anomaly previously observed6 inthe resonance region persists to higher energies. No otherfree parameters enter into the calculation. Phase shifts upto f = 5 due to Arndt7 were used in the calculation.Effects due to spin-flip were included.

In Fig. 1 are shown our results for elastic scatteringof 800 MeV/c incident pions compared with the data ofMarlow et ai.^ The calculated angular distribution agreesremarkably well both in shape and magnitude with thedata, particularly if one notes we have fixed all parametersa priori and not varied in order to achieve a betteragreement with experiment. The experimental results are

10

I02

CO

a10',o -

•o

10

10'

"vV

f

a 2 = 0.39

c

Jm2

12C800

\

\

v• IIi

i ji /w

(?t+, J I + ) I 2 C :

MeV/c

i\\

20

"cm

40

Fig. 1. Differential cro.s.s section in the center-of-masssystem assuming partial waves through / = 5 fornC(iiJr.KJt)]2C scattering for 800-MeV/c pions; tin-experimental data are from Marlow et al.-* Thecontribution from spin-flip is included.

ResearchTheory

slightly higher than theory for small angles and thetheoretical minimum is deeper than experiment.However, no Coulomb effects that would mitigate thediscrepancies have been included in this calculation.

We have found the f wave to become significantabove 400 MeV. Unlike single and double chargeexchange. s however, the g and h wave only begins tohave an appreciable contribution above 900 MeV.However, these partial waves become important forinelastic scattering to the 2+ state of ' -C at essentiallythe same energies as for the charge-exchange reactions.

In Fig. 2 are shown results for excitation of the 2+ of' -C by 800-MeV/c pions, which are compared with datafrom Marlow et al.^ Results of three calculations aregiven. The first employed no quadrupole enhancement anda value of a - = 0.39. This calculation seriouslyunderestimates the data. The second calculation employed

(010°

•g 10-1

a 2 = 0.34p=1.5

v j

I T

f

a2 = 0.39p = 1

12C (7T, Jt')12C800 MeV/c

a 2

t> p =

%

i

= 0.391.5

V T

IT.

\

20 40

e,cmFig. 2. Differential cross section in the center-of-masssystem for (TZ.K'I inelastic scattering to the 2+ level of^Cfor H0U-MeV/c pions; the experimental data are fromRef. 3. The theoretical curves are for a- - 0.39 fm~-(dash-dot curve), fi = I. a2 = 0.39 fhr2, fi =1.5 (clottedcurve), and a2 = 0.34 fin"2, P = 1.5 (solid cune). Partialwaves up to I = 5 were included.

PR 91 IV PionlndElas-2

the same value of a.~ but used a quadrupole enhancementof 1.5. The resulting curve is much closer to the data,although there is still disagreement for the most forwardangles. Finally, the third calculation used a smaller valueof a - (0.34) and an enhancement of 1.5. Aliiiough wehave not attempted to fit the data, of the three this lastcurve most nearly follows the experimental points. Theuse of a smaller a - may simply be compensating for thetail of the harmonic oscillator wave functions: use ofWoods-Saxon single-particle wave functions would havethe same effect as using a smaller value of a-. The shapeof our calculated angular distribution is similar to that ofthe original calculations described by Marlow et al..-^ whoused the distorted-wave Born approximation (DWBA) todescribe the reaction.

In Fig. 3 are plotted the ratios of a(7iTn) to a(7t+n)for inelastic pion scattering to the lowest 2 + and 4 + of

F/i;. .?. /?«/<>; of the forward-angle cross section for K to7t+ excitation of levels in lfiO as a function ofbombarding energy. Effects of spin-orbit are included.

ResearchTheory

18O as a function of the pion kinetic energy. The angulardistributions for n~ and for 7i+ are nearly identical and theresult plotted in Fig. 3 is the ratio at zero degrees. Thecurve labeled (3 = 1 represents results assuming noadditional effective charge and the curve labeled p = 1.5was obtained using a value for the quadrupoleenhancement consistent with the results of both E2transitions and pion inelastic scattering. Thus, varyingthe pion kinetic energy should provide a useful probe of"isospin mixing of the nuclear wave functions, as well asproviding a means to study the propagation through thenuclear medium of hadrons other than the A.

References

1. S. H. Rokni, H. W. Baer, A. G. Rergmann, J. D.Bowman, F. Irom, M. J. Leitch et al., Phys. Leu. B202, 35 (1988).

2. A. L. Williams. L. Agnew. L. G. Atencio. H. W.Baer, M. Burlein, G. R. Burleson et al.. Phys. Leu.5 216. 1) (1989).

3. D. Marlow. P. D. Barnes. N. J. Colella. S. A.Dytman, R. A. Eisenstein. R. Grace et al., Phys.Rev. C30. 1662 (1984).

4. S. Cohen and D. Kurath, Nucl. Phys. 73, I (1965).5. C. W. de Jager, H. de Vries, and C. de Vries. Atomic

Nuclear Data Tables 14, 479 (1974).

6. C. Wilkin, Nuovo Cimento Leu. 4, 49! (1970); T.S. H. Lee and D. Kurath, Phys. Rev. C21. 293(1980).

7. R. Arndt, computer code SAID, Phys. Rev. D 28, 97(1983).

8. E. Oset and D. Strottman, Phys. Rev. C 4 1 . 2356(1990); E. Oset and D. Strottman, "High EnergyPion-Induced Double-Charge Exchange and IsovectorRenormalization," Los Alamos National Laboratorydocument LA-UR-92-1681 (submitted to PhysicalReview Letters, 1992).

ResearchTheory

Production of r| mesons by pions

L. C. Liu (Los Alamos)

Near-threshold r) meson production from nucleiproceeds almost entirely via the excitation of the baryonresonance N*(1535) and its subsequent decay to the x\-nucleon channel. Consequently. 1"| can be used to tag thenuclear dynamics of the N*( 1535), for which the presentknowledge is next to nil. Not only can this dynamicsenrich the current understanding of the hadronic structureof N*< 1535) and r\. but also it can provide independenttests for the basic physical principles that have been usedin modeling the interactions between nuclei and theA( 1232) resonance.

The reaction 7t~ + *He —> r| + t(g.s.) was studied byPeng et al. at LAMPF, using pions having laboratorymomenta between 590 and 680 MeV/c.1 Although thetheoretical calculation based on the distorted-wave Bornapproximation (DWBA) gave correct angular dependence(not shown here), it underestimated the data by factorsranging from 1.5 to 2.9.' Large discrepancies betweendata and DWBA calculations were equally noticed for thep + d —> r\ + -*He reaction near threshold.- The strongdisagreements between data and DWBA have motivated usto investigate the dynamics of nuclear eta production inmore details. The reaction • He(7t~.V|)t(g.s.) offers severaladvantages over other nuclear reactions: (a) V) productionby (real or virtual) pions is the driving mechanism forhadron-induced r\ production in the threshold region:(b) Both the -̂ He and tritium are very light nuclei.Hence, nuclear-medium modifications of the elementarymeson-nucleon amplitude are unimportant and can beneglected. This greatly reduces the model-dependence ofthe theoretical analyses: (c1 The antisymmetrization of thenucleons is only in the spin-isospin sector. Thus, the

implementation of Pauii blocking of the in-mediummeson-nueleon scattering becomes trivial.

In the distorted-wave theory, the production crosssection is given by

d o

2ft k (1)

where k' and k are the cm. momenta of the eta and thepion. The \\i and % are the distorted waves in theincoming and outgoing channels, and V is the TT —> 1"|transition potential. In DWBA, V is given by the first-order meson-nucleus interaction

v(1> = j(k'.q'|tnjk,q><t)*(q')<l)<q)

5(k' + q ' - k -q ldq'dq . (2)

which we shall denote, for succinctness, as ft^jcp'''. withp( '> (= 0*<])) representing the single-nucleon densityfunction. The integration in Eq. (2) represents a completefolding of the TCN —> r|N t-matrix with the single-nucleonwave functions.-* Further, the distorted waxes i|/ and x aregenerated with first-order n-nuclcus and r)-nucleus opticalpotentials (to be denoted, respectively, as w ( ' ' and u*'').These optical potentials have a structure similar to that ofv1' >. namely. w('> = jtn7Ip<' > and u ( ' ' = JinT,p<'>. Withthe use of the meson-nucleon amplitudes l}^n. i ^ . andlnn given by the dynamical model of Ref. 4. the first-order interactions can all be calculated microscopically.However, as has already been mentioned, the DWBA alonecannot fully account for the data.

Because of the strong coupling existed between theTtN and l"|N channels, the etas can also be produced via

Research

two-step processes that involve a pair of nucleons. such asJINN -> nNN -> i]NN and JINN -> r|NN -H> r,NN. We

have investigated all possible second-order processes,which we denote schematically by

and

.2)

(4)

(5)

where the variables of integrations are not explicitlywritten for the sake of simple notation. In theseequations. QGoQp^ = G o p ( 2 ) - P G ( ) /

) p ( ' >p ( ' ' • TheGo is the free meson-nucleus Green's function and isdiagonal with respect to the projectors Q and P thatproject the nucleus onto its excited and ground states,respectively. The p ' - 1 and p^~'are the shell-model anddynamically correlated two-nucleon density functions.The subtraction of the ground-state contribution. PG()P. isnecessary in order not lo double count the contributionsassociated with the iteration of the first-order interactionsw 1 ' ' and u ( ' ' . which are contained in the vj/ and X- Themultidimensional integration required by the second-orderinteractions was carried out with the folding proceduregiven in Ref. 5. Our calculations show that the secondterms of w'- ' and u '- ' are numerically unimportant. Thisis because they all involve twice the large momentum-transfer processes n <=> r|. The second term of v'-1 isalso very small because of the inequality

l n 7i

lnnIn Fig. I. the data obtained with pion laboratory

momenta 590. 600. 620. 650. and 680 MeV/c arerepresented respectively, by filled squares, triangles,crosses, filled circles, and open circles. Theoretical resultsobtained with V = v1'> + v'- ' . W = \v ( ' ' + w1-1. and U =u ( ' ' + u1-1 are shown in Fig.l as the dot-dashed, dashed,solid, chain-dotted, and dotted curves in ascending order ofpion momentum. The agreement between the theory anddata is now very good: perhaps with the exception at680 MeV/c. where the theory is slightly below the data.

The increase in the calculated cross sections withrespect to the DWBA result of Ref. I is due primarily tothe contribution from the first term of v'-1 . which isabout 30-40% of that of v ( ' ' and is "in-phase" with thelatter. This constructive interference between the one- andtwo-step processes is responsible to ai1 increase of a factorof about 2 to 3 in the theoretical cross sections, large

Theory

enough to compensate the slight cross-section reductioncaused by the inclusion of the second-order distortingpotentials. We have also investigated three-nuclconprocesses. Because of the destructive interference amongthese processes, their net effect is very small.

The excellent agreement between theoretical resultsand the data as obtained in this analysis is strong evidenceof important nucleon-pair effects in nuclear eta production.We conclude that, in addition to the direct one-slepmechanism in which the t] production takes place on anucleon in the nuclear ground state, the two-stepproduction mechanism is equally important. We havenoted that the dominant two-nucleon contribu'.ion is dueto the two nucleons coupled to J = 0 and 1 = 1 .

As a final remark, we emphasize that two-stepprocesses are. in general, much less important than first-step processes. This is indeed the case with processesinvolving the iteration of the same elementary meson-nucleon interaction, such as ir| r|C?G o(? tr)r) or

However, for the 71 —> 11 transition, the

ib /

sr)

TJ

0"O

10'

100

** — A v

- - -

A

10 20

"cm

• ~~~—. i .^ ,. • »~~

30 40 50 60

(cleg)

I'if!. I . T h e K + •''He — > } } + t ( f ; . x . ) m i l l i o n t i l p i o n

laboratory momenta 590, 600. 620. 650. ami 6S0 MeY/c.In ascending order of the pion momentum, the data areshown as the filled squares, triangles, crosses, tilledcircles, and open circles. Theoretical results obtained withthe inclusion of inelastic-channel coupling are gi -n.respectively, as the dot-dashed, dashed, si'lid. chain-dotted,and dolled curves.

ResearchTheory

two-step process is given by l\]nQ^oQlKn- which is not asimple iteration of the same elementary amplitude i^n.Rather, il is the folding of two different amplitudes withI lirrc » I [r|H • '• 's- therefore, not surprising that this

two-step process can contribute as importantly as the one-step process.

We formulate the following proposition: If the first-order (or one-step) mechanism involves an elementaryprojectile-nucleon amplitude ,4. and the second-order (ortwo-step) mechanism involves the folding of /\ withanother projectile-nucleon amplitude B. with B beingmuch stronger than A. then the contribution of thesecond-order mechanism will be important and must notbe neglected. We believe that this rule, being quitegeneral, is applicable to a broader range of nuclearreactions than the pion-induced x\ production on nuclei.

References

1. .1. C. Peng. M. J. Leitch. J. D. Bowman. F. Irom. J.Kapustinsky. T. K. Li et al.. Pins. Rev. Leu. 63.2353(19X9).

2. J. Berger, M. Boivin. A. Boudard, P. Fleury. J. F.Germond, L. Goldzahl et al.. Pliyx. Rev. Lea. 61 .919 (1988).

3. L. Celen/a. L. C. Liu. and CM. Shakin. Pliyx. Rev.C 11 . 1593 (1975) and Phys. Rev. C 12. 1983(1975).

4. R. S. Bhalerao and L. C. Liu, Phyx. Rev. Leu. 54.865(1985).

5. Q. Haider and L.C. Liu, Z Phyx. A 335 . 437(1990).

ResearchTheory

Report of the T-5 theoretical group

R. R. Silbar (Los Alamos)

Quarks and QCD

Substructure Effect on Meson-Meson Mixing

We have studied the effect of quark substructure onthe strength of pco mixing as a function of the square ofthe four-momentum of the meson. We find that the effectof such substructure is to introduce a significant variationabsent in the fixed mixing amplitude assumption that isconventional. The effect depends very weakly on the scalein the meson —> quark-antiquark amplitude ("size" of thewave function) and only slightly more strongly on thequark threshold taken in the calculation, which consists oftaking into account the quark-loop contribution to themixing propagator for the mesons.

The effect of this momentum dependence on thecontribution of pco mixing to charge symmetry breaking(CSB) is disastrous: an amplitude fitted to theexperimental point in the time-like region contributes lessthan one-fifth of the CSB amount found in theconventional momentum-independent approach. Weemphasize, however, that the conventional assumption istotally unjustified for extrapolations in the square of thefour-momentum, much larger than a few times the squareof the mass of the pion.

We have now confirmed the systematics of this effectin a bosonic-loop calculation. Maltman has claimedsimilar results for n^f] mixing using loops in chiralperturbation theory. We hope to check that result also, ina quark-loop calculation, in the coming year.

Exotic States in a Relativistic Quark PotentialModel

We have begun an effort to add other SU(3)flavorchannels to our AA bound state calculation in the T = 0,J = 3 channel reported earlier. So far, we find that thesemix very little with this state, reducing our mass estimatefor it by only about 20 MeV.

Nonrelativistic Quark Model andBaryon-Baryon Phase Shifts

With our Chinese collaborators, we have applied ourideas for quark descriptions of nuclei (see below) to thebaryon-baryon interaction in a nonrelativistic model. Aconventional harmonic oscillator model is used to describeconfinement of quarks in an isolated baryon, and a standardnonrelativistic description of the color-magnetic spininteraction between quarks is included. When two baryonsare near each other, however, a variational parameterdescribes the amplitude for tunneling from the wavefunction of one baryon to that of the other. In addition, ascreening factor is applied to the oscillator potentials for aquark from one baryon in the region intermediate to theother.

Defining the baryon-baryon potential as theminimum energy attained by varying the tunnellingparameter at fixed separation b ween the two baryons, wefind an attractive intermediate-range interaction in thenucleon-nucleon system and a very strong attractive

ResearchTheory

potential between two A's in an isospin-0 configuration.In fact, the ^S} channel shows the same dibaryon that weand others have found previously in relativistic potentialand bag models. Using standard techniques to computephase shifts in this model, we find that the ' So phaseshift can be accurately fitted to data over energies fromnear zero up to several hundred MeV by fixing thescreening parameter to a value within the expected range.The -̂ Sj phase shift then has the same energy dependenceas the data, but is somewhat more attractive overall. The'DT phase shift also agrees well with data.

Nuclear QCD

We have extended our quark description of nuclei fromthe A = 4 case to the A = 3 case. We find consistency inthat the A = 3 binding energy is smaller than that foundpreviously in the A = 4 system.

In our model, nuclei are described directly in terms ofsingle-body quark wave functions. These wave functionsare defined with respect to a mean-field potential,consisting of a set of linear scalar potentials with originslocated on a defined spatial array (regular tetrahedron forA = 4. equilateral triangle for A = 3). The overall spatialscale of the array is used as a variational parameter. Therise of each potential is truncated at the plane midwaybetween any pair of origins. The combined potential thusdescribes the tendency for quark localization in QCD toregions of size =1 fm and confines quarks to the overallregion of the nucleus.

We next evaluate the single-body energy using thispotential in a Dirac Hamiltonian. The trial wavefunctions are weighted sums of solutions of the Diracequation for an isolated linear scalar potential at eachorigin. The relative weights are used as variationalparameters. The wave functions are first isospin- andcolor-correlated into "nucleons" and then pairwiseantisymmetrized over the entire nuclear wave function.To the one-body energy, we add the two-body interactionenergy from (relativistic) color-magnetic gluon exchangeusing a limited range propagator for the gluons.

In the A = 4 case, we found a minimum energysystem of nuclear size. 20 ± 10 MeV of binding energy(with the variation correlated to the range parameter for thegluon propagator), and a deviation of the quark probabilitydistribution of several percent from that for isolatednucleons. Our new A = 3 results are very similar, withbinding energies now 3 + 3 MeV. This systematicagreement with data is very encouraging.

In the coming year we hope to analyze the deep-inelastic structure functions for these systems. An EMCeffect is expected in the valence quarks, consistent withthe Fermilab E772 results, but quantitative results remainto be determined. In the longer term, we will be studyingmethods for extending our approach to larger nuclei andthe effects of more sophisticated models of the confiningpotential.

Gluon QCD

We have also studied the formation of a chirallysymmetric color octet of scalar and pseudoscalar glueba'ls.A 0-model-like structure is found, where the gluoncondensate appears as the analog to the a field and mixeswith it. The analogy suggests that the difficulty inobserving the lowest mass color-singlet glueball state issimilar to that for the a meson. Going further, thenonlinear o model suggests not linearizing the colormultiplets. If the color-octet scalars are massless, theeffect of exchanges of these scalars has the right propertiesto produce (using the one-boson-exchange approachfamiliar to nuclear physics) a quark- and gluon-cnrifiningscalar potential, dominating that from "one"-gluonexchange and consistent with spectral observations inheavy-quark systems.

Hadronic Field Theory and Scattering

Monte Carlo Approaches to Effective FieldTheories

We have recently been exploring the applicability ofMonte Carlo methods to solve effective field theories.During the past year we have developed Monte Carlomethods to solve some field theory problems exactly. Forsimplicity, our first applications have been to simpleproblems, including nucleons interacting through scalarmeson exchange. During the course of this work we haveobtained "exact" solutions to the polaron problem, a long-standing effective field 'heoiy model from condensedmatter physics. The methods we have developed allow usto solve for the ground-state energy and effective mass forthe one-fermion problem, and then to solve for low-lyingstates in few-fermion problems. This method should beapplicable in a wide variety of areas, including low-energyJiN scattering and various light-cone quantized fieldtheories. We are currently exploring these applications.

98

Research

Hadron-Hadron Scattering Amplitudes to AllOrders in Meson Exchange

As the number of colors in QCD, Nc, becomes large,it is possible to sum up all meson-exchangecontributions, however arbitrarily complicated, to meson-baryon and baryon-baryon scattering. A semi-classicalstructure for the two-flavor theory emerges, in closecorrespondence to vector-meson-augmented Skyrmemodels. In this limit, baryons act as extended staticsources for the classical meson fields. This leads to non-linear differential equations for these meson fields, whichcan then be solved numerically to find the static, radial(hedgehog-like) solutions.

The nonlinear terms in the equations of motion forthe quantized meson fields can then be simplified, toleading order in 1/Nc, by replacing all factors of themeson field but one by the previously-found classicalfield. This results in linear, Schrodinger-like equations forthe scattering wave functions, which can be solvednumerically in the usual way. The asymptotic solutionsfor each partial wave then give the phase shifts for thescattering. For the meson-baryon case, these phase shiftspredict the baryon-resonance spectrum of the model.

Earlier, we carried out a first stage of thiscalculational program for the simple case of O mesons andnucleons only. More recently, our computer programshave been extended to deal with the complications ofisospin and pseudoscalar mesons. However, a modelinvolving only pions and nucleons (the "nucleon" isactually a tower of I = J nonstrange baryons: N, A, ...)does not give any higher nucleon resonances; the effectivertN potential is, in this case, strictly repulsive.

We are now implementing the next stage in thisprogram, treating a more realistic world consisting of nand a mesons interacting with the nucleon (tower). Sucha model, based on the linear-c model, will respect chiralsymmetry and should have the requisite attraction to givean interesting baryon spectrum.

Soft-Photon Approximation in Hadron-HadronBremsstrahlung

Low pointed out long ago that a bremsstrahlung crosssection for the process a + b—>a + b + y can be writtenas a series in terms of the photon energy k

o= B + Ck

Theory

where the coefficients A and B can be expressed in termsof the on-shell elastic ab —> ab scattering amplitude. Thisobservation offered interesting insight, and it led to use ofthe first two terms in the expansion (the soft-photonapproximation) as a basic tool for analysis ofbremsstrahlung measurements.

However, the external-emission diagrams, whichdescribe the bremsstrahlung processes, do not correspondto a single, unique set of on-shell kinematics for theinitial or final state. Low suggested one possible choice,SL = (si + sf)/2, at which to evaluate the on-shellamplitudes, but clearly this choice is not unique.Whatever choice is made, it is obvious that A, B, C, ...,depend implicitly upon k, because the various on-shellkinematic choices are related to k by energy-momentumconservation The powers of k in the expansion of oexhibit the explicit dependence on k, and the functionaldependence of the coefficients upon k denote a furtherimplicit dependence coming from our choice of the on-sheli point.

The soft-photon expansion is exact in the sense thatretaining all terms in the expansion leads to a correctresult (assuming that the series converges). However,each choice of s at which one evaluates the on-sheilamplitudes that determine A(k), B(k), .... will result in adifferent expansion. Because there is no dimensionlessparameter in which to expand, there is no a priori reasonto argue that the soft-photon expansion must convergerapidly, and, therefore, that any particular soft-photonapproximation (i.e., A(k)/k + B(k) for a given choice ofon-shell s) must necessarily be a good one. Specifically,Low's choice of SL for the soft-photon approximation toJtp —> 7ipy leads to a result that agrees with the data foronly the first 30 MeV and fails completely in theresonance region. Furthermore, while the conventionalLow soft-photon approximation provides an excellentdescription of pp —> ppy data, it fails to describe np —>npy, where meson-exchange currents provide a dominantcontribution to the physical process.

We advocate a procedure that we believe will producereliable soft-photon approximations, even when one has aresonance structure in the elastic-scattering cross sectionor when meson-exchange currents play a significant role.The choice of kinematics to be used should rely upon areduction of the bremsstrahlung amplitudes to their treediagram (e.g., one-boson exchange for NN scattering)limit. One should utilize the full set of initial-state andfinal-state variables defined by the on-shell kinematics inthe external-emission diagrams as well as the u-channel-exchange nature of the internal-emission diagram in the

ResearchTheory

tree limit. In this manner, we can incorporate into thetwo leading terms of the soft-photon expansion theessential elements that describe the bremsstrahlungprocess.

A program is now under development to be used inthe analysis of the neutron-proton bremsstrahlungmeasurements planned at LAMPF by the PhysicsDivision at LANL. The aim is to explore the meson-exchange-current contribution to nucleon-nucieonbremsstrahlung in the energy range J 00-400 MeV. Such•.ffects are absent in the proton-proton bremssirahlungexperiments that have been carried out at TRIUMF.

Few-Body Nuclear Physics

Triton Binding

We have translated recent progress in understandingthe nucleon-nucieon force into progress in understandingthe trinucleon systems. Several years ago it was shownthat the bulk of the potential energy in the trinucleonsystems arises from the tensor force. Subsequently, itwas shown that the tensor force accounts for roughly two-thirds of that energy in 3H, 3He, 4He, and I6O. It wasalso shown that a suitably defined one-pion-exchangepotential (OPEP) could account for much of the potentialenergy. This is not too surprising in view of OPEP'slarge contribution to the tensor force.

New calculations have decomposed the trinucleon anda-particle potential energies from several potential modelsinto their component parts. Roughly 80% of that energyconies from OPEP, demonstrating that it is the singlemost important force component for the few-nucleonsystems.

In addition, the Nijmegen group has recentlyperformed by far the most accurate phase-shift analysis fornp and pp scattering. Fitting the (neutral and charged)pion masses in OPEP to the nucleon-nucleon (NN)scattering data reproduces the (different) free pion masseswith approximately one percent error bars. The NN force,which reproduces the data, gives a triton binding energy of7.66 MeV, smaller than the experimental value of8.48 MeV. This is much smaller than the bindingproduced by the Bonn-A model (which does not fit the NNdata very well). This result is significant because theNijmegen-91 potential produces a high-quality fit to theNN data.

Microscopic Studies of ^H e

The low-lying noc scattering resonances are thesmallest A states that allow one to study L • S splittings.In traditional potential models, these splittings arise fromthe two- and three-nucleon interactions, while inrelativistic mean field models, they arise primarily fromthe large vector fields, which are greatly enhanced inmatter. We are undertaking Green's function Monte Carlocalculations of ^He in order to understand to what extenttraditional potential models can describe the L • Ssplitting. Our results indicate that approximately 80% ofthe splitting can be obtained with realistic two- and three-nucleon forces, with the two-pion-exchange three-nucleoninteraction making a significant contribution to thesplitting. Much of the difference between experiment andtheory can be accounted for phenomenoJogicaJly byaltering the short-range part of the three-nucleoninteraction. This short-range part is difficult to determinetheoretically.

This work is continuing; we are currently exploringdifferent models of the three-body force and the possibilityof trying to model an enhanced vector meson field.

Nuclear Physics with Strangeness

Light Hypernuclei and the Hyperon-NucleonInteraction

We are engaged in a long-term study of the hyperon-nucleon (YN) interaction and light hypernuclei. In thiswork we have employed "realistic" YN interactions andstate-of-the-art variational Monte Carlo methods to studythe ground and low-lying excited states of four- and five-body hypernuclei. Earlier studies revealed the tremendousimportance of the coupling of the AN and SN channels.The most recent Nijmegen one-boson-exchange interactionreproduces the four-body ground-state energy fairlyaccurately in these calculations. However, the strongAN-SN coupling in the triplet channel produces aneffective interaction too weak to reproduce the binding ofthe spin-1 excitation in A = 4 or the spin-0 ground state

Is There a INN Bound State?

During the past year we have extended our studies tothe S~nn system. There have been tantalizingexperimental indications of I hypernuclear bound states in

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few-body systems. Due to the strong coupling betweenthe Z and A channels, it is difficult to determine whethersuch features shoi'ld be interpreted as true bound states oras threshold effects just below the Z threshold. The Z~nnsystem is the simplest and most attractive possibility fora bound Z hypernucleus that cannot decay via strong Z-Aconversion in the nuclear medium, and so is a naturalcandidate to investigate. We have found that the Z~nnsystem is not bound using the Nijmegen model YNinteractions, even if the nn force is artificiallystrengthened to produce a bound dineutron. In the future,we hope to be able to extend these calculations to the A =4 system, where experiments have seen peaks belowthreshold.

Narrow Structure in Ad Scattering near theI Threshold

At the 1989 Padova Strangeness Conference, theJapanese reported that the spectrum from stopped K~ inthe reaction 4He(K~.7i~) exhibited narrow structure belowthe threshold for Z production. Furthermore, no suchpeak was observed in the spectrum from thecomplementary 4He(K~,7r+) reaction, implying that thestructure was T = 1/2. Recent Brookhaven results from anew in-flight K~ experiment confirm the structure in the(K~,Jt~) reaction and lack of structure in the (K~,Jt+)reaction observed in the stopped K~ measurements. Thisstructure has been interpreted as a Z bound to thetrinucleon core by about 3 MeV with a decay width ofsome 8 MeV. Therefore, we have investigated thepossibility of the existence of an A = 3 (T = 0, S = 1/2)ZNN bound state. Such a state would be directlyobservable in A-deuteron scattering or in the 3H(K~~,Jt~)reaction.

To examine the possibility of an A = 3 bound state,we have calculated the total S-wave Ad elastic andinelastic cross sections in the region of the Z-productionthreshold using AN-ZN coupled-channei, separablepotentials in a Faddeev-type formalism. We havediscovered that two different YN potential models producestructure in the Ad cross sections, structure that lies belowthe Z threshold. To understand this structure, we haveextended our code to extract the pole in the YNNamplitude in each case. In the first case, the ZNNeigenvalue corresponds to a pole that lies below threshold(bound), whereas in the second case the pole lies above thethreshold. That is, we have demonstrated that structure inthe cross section below the Z threshold does not by itselfguarantee that a ZNN bound state exists.

Theory

Nuclear Structure

F-Spin Admixtures in Nuclei

If neutrons involved in collective motion in heavynuclei are converted into protons, is the resultingcollective motion changed in any way? We have shownthat if the deformation parameters of protons and neutronsare the same, then the collective motion remains invariantunder interchange of neutrons ant' protons. In theinteracting boson model of nuclei this symmetry can berelated to a quantum number called F-spin, and the mostsymmetric states have maximal F-spin. This symmetry isvery different from isospin, since F-spin relates the spectraof low-lying states ot neighboring nuclei, while isospinrelates the spectra of excited states, i.e., isobaric analogs.

Using the difference in the neutron and protondeformations parameters of 16^Ho measured in a recentpion single charge-exchange experiment at LAMPF, theamount of non-maximal F-spin admixtures is at least 6%.This differs from estimates based on B(M1) strengths,which give 2 to 4%.

A more systematic study of F-spin symmetry can beundertaken when the new neutral-meson spectrometerbecomes functional at LAMPF by studying the pion-charge-exchange transition from the ground state of aneven-even nucleus to the analog of the first excited state(which occur via a quadrupole isovector transition andhence are sensitive to the difference in quadrupoledeformation parameters). We have also shown thatanother sensitive measure of F-spin admixtures aremagnetic moments of the y-vibrational band compared tothose of the ground-state band.

A Sum Rule for S(M1) Strength

Since the discovery of an Ml orbital mode, the"scissors mode," there has been a systematic study of Mlstrength for a variety of nuclei by electron and photonscattering. We have derived a sum rule for B(M I) strengthwithin the interacting boson model, which states that thetotal strength is proportional to the total number ofquadrupole bosons (i.e., pairs of valence nucleons withangular momentum J = 2) in the ground state. Thenumber of quadrupole pairs is directly related to thenuclear deformation.

Comparing this sum rule with a collection of Mldata, we find that the number of quadrupole pairs increasesas the number of total valence pairs increases, but thenbegins to decrease before the middle of the shell is reached.

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This means that the nuclear deformation is beginning todecrease before the middle of the shell is reached, which isunexpected. In turn, this implies that either all Mlstrength has not been measured or other degrees of freedomare becoming important in the ground state, e.g., pairswith angular momentum J = 4. With the new neutral-meson spectrometer, pion single charge exchange may bea good probe for studying the orbital Ml strength, sincethe reaction is isovector and, at small angles, orbital innature.

K-Quantum Admixtures in the NeutronResonance Region

A recent publication claimed incomplete mixing ofstates with different K-quantum numbers in the neutron-resonance region of heavy nuclei. We have shown thatsuch a claim leads to a serious discrepancy with thestatistical model. As a consequence, we have re-examinedthe experimental data on which the claim is based andhave found that the totality of the evidence invalidates theclaim that K-mixing in the resonance region isincomplete. In fact, the resulting K-admixtures agree withthose predicted by the statistical model.

Weak Interactions

Decays

The decays r\ —> nlvt {( = e,ji) probe some classesof new charged-current sernileptonic interactions. Theyoccur in the Standard Model but only due to G-paritybreaking effects (i.e., electromagnetic corrections and themass difference of the u and d quarks). The correspondingbranching ratios are expected to be of the order of 10"'^.Neglecting G-parity violation, r| —> KN/ can receivecontributions only from first-class scalar, second-classvecto>, and second-class tensor interactions.

We have investigated the available empiricalinformation on the interactions that can contribute tothese decays and have considered the implications for theirbranching ratios. We find that searches for r\ —> neve

with a sensitivity to branching ratios below 10~8 to10~9 (-3 x 10"1 ' ) and for r\ -» TtjaVjj with a sensitivityto branching ratios below IO~7 to 10~8 (~1(T9) wouldgive new information on second-class (scalar-type)interactions involving the electron and the muon,respectively.

Muonium to AntimuoniumExotic Decay / i + -> e+'VeVSymmetric Models

Conversion and thein Left-Right

Muonium to antimuonium (M —> M) conversion andthe exotic muon decay |a+ -> e+v ev u are forbidden in theStandard Model, since they violate the conservation ofelectron and muon numbers. Recent experiments have setimproved limits on the rates of these processes.Considerably more sensitive searches for (M —» M) and| i + —> e+VeV^ will be carried out in the new generationsof experiments presently planned or under way.

We investigated these two processes in left-rightsymmetric S U ( 2 ) L X S U ( 2 ) R X U(l ) B L models withtriplet Higgs bosons. Left-right symmetric modelsprovide an attractive framework for understanding theorigin of parity violation in the weak interactions. Theclass of S U ( 2 ) L x S U ( 2 ) R X U ( 1 ) B - L models with triplet

Higgs bosons can also provide an explanation of thesmallness of the masses of the observed neutrinos. Wepointed out that in these models there is a lower bound onthe rate for both processes for the range of the muonneutrino mass, mV(i, for which cosmological constraintsrequire v u to be unstable.

For the strengths G + + and G+ of the effective M -»M and \i+ -> e + v c v u interactions we find | G + + I > 2 x10~ 4 Gp and | G + | > 4 x 10~4 Gp for the range36 keV < mV|i < 270 keV (which we find to be theallowed range for unstable v u ' s in the model). Thesebounds are not far from the limits expected from the newexperimental searches. The present experimental upperlimits are | G + + \ < 0.16 Gp (90% C.L.) and I G+ | <0.067 G F (90% C.L.), respectively. The lower boundsincrease with decreasing mV | r Thus, as the experimentallimits on | G + + | and/or [ G+ | become more and morestringent, the allowed range of i r ^ for which the modelis viable becomes increasingly smaller.

Other Physics

Fractional Quantum Hall Effect

A century ago Hall discovered that when a current ispassed through bulk material in the presence of a magneticfield, an electric field appears in a direction perpendicularto both the current and the magnetic field. The Hallresistivity is this electric field divided by the originalcurrent and is predicted to have a linear dependence on themagnetic field.

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This prediction is confirmed. However, at lowtemperatures, plateaus in the linear dependence areobserved in the Hall resistivity as a function of magneticfield for certain values of I he magnetic field. Some ofthese plateaus arise from a quantum effect in which theFermi level of the electrons lies between the Landaulevels, which are the quantum single-particle levels forelectrons in a magnetic field. In other words, plateausoccur when the electrons are in closed shells. What ismore surprising is that plateaus also occur for certainfractional filling of the Landau levels, that is, when theshells are not closed.

Using the concepts and techniques of the nuclear shellmodel, we are diagonalizing the Coulomb interactionbetween electrons to see if the many-electroneigenfunction will produce plateaus in the Hall resistivityfor fractional filling of the Landau levels.

Dark Matter and Quantum Gravity

For some time, we have been studying thephenomenological implications of quantum gravity. Wehave now shown that, if the renormalization groupequations for Newton's constant (in a higher derivativeextension of Einsteinian gravity) apply in the infraredregime, then it increases with increasing distance scale, ina fashion similar to the growth of the strong couplingconstant in QCD. In the gravitational case, however, a 1-cm scale constitutes a "short" distance. We find thatparameters of the theory can be chosen so that thevariation of Newton's constant is less than a few percentbetween such a scale and the scale of the solar system, butthen begins to increase rapidly as the scale grows to thatof the galaxy and the universe.

The "Dark Matter Problem" arises by comparingobserved accelerations in the universe with those expectedfrom the observed matter density and the value ofNewton's constant measured on laboratory scales. Ourcalculations suggest that instead of postulating theexistence of large amounts of non-baryonic ("dark")matter, the observed accelerations may be explained, atleast in part, by a larger effective value of Newton'sconstant on these large-distance scales. However, avariation of even a few percent over the solar system isnot in good agreement with experimental data. In thecoming year, we intend to study other quantum gravitiesto see if similar results at large distances can be obtained,which are also consistent with this regime.

Group T-5 Publications

B. R. Barrett, R. F. Casten, J. N. Ginocchio, T.Seligman, and H. A. Weidenmilller, "Is There IncompleteMixing of States with Different K Quantum Numbers inthe Neutron Resonance Region?," Phys. Rev. C4S,R1417 (1992).

J. Carlson, "Monte Carlo Approaches to Light Nuclei:Structure and Electron Scattering," Nucl. Phys. A 522,185c (1991).

J. Carlson, "Three-Nucieon Interactions in A = 4 & 5Systems," in Proc. of the Workshop on the NuclearHamiltonkm and Electromagnetic Current in the 90's(1991).

J. Carlson, V. R. Pandharipande, and R. Schiavilla,"Many-Body Theory of Electron-Nucleus Scattering:Light Nuclei," in Modern Topics in Electron Scattering,B. Frois and I. Sick, Eds. (World Scientific, Singapore,1991), p. 177.

J. Carlson, D. O. Riska, R. Schiavilla, and R. B.Wiringa, "The Weak Proton Capture Reactions on 'H and3He and Tritium (3 Decay," Phys. Rev. C 44, 619 (1991).

J. Carlson and V. R. Pandharipande, "On the Absence ofExotic Hadrons in Flux Tube Quark Models," Phys. Rev.D',X 1652(1991).

J. Carlson and K. E. Schmidt. "Monte Carlo Approachesto Effective Field Theories," in Recent Progress in Many-Body Theories VII, Los Alamos National Laboratorydocument LA-UR-91 -3023 (1991).

J. Carlson and R. Ransome, "Hyperon-NucleonInteraction," in the P1LAC Users Group Report, Physicswith PILAC, D. J. Ernst, Ed., Los Alamos NationalLaboratory document LA-UR-92-150, p. 101.

C. R. Chen, G. L. Payne, J. L. Friar, and B. F. Gibson,"Nd Zero-Energy Scattering," Phys. Rev. C 44, 50(1991).

J. L. Friar, "Few-Body Systems," in Modem Topics inElectron Scattering. B. Frois and I. Sick, Eds. (WorldScientific. Singapore. 1991), p. 104.

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J. L. Friar, "p-d Capture Reactions in MuonieMolecules," in Xllhh European Conference on Few-BodyProblems in Physics (Springer-Verlag, Vienna, 1992),p. 304.

J. L. Friar, "n-d and p-d Capture Reactions at ExtremelyLow Energies," in Proc. of the Workshop on the NuclearHamiltonian and the Electromagnetic Current for the 90's(1991).

J. L. Friar, "New Approaches for Bound and ScatteringStates," in Xlllth European Conference on Few-BodyProblems in Physics (Springer-Verlag, Vienna, 1992),p. 538.

J. L. Friar. B. F. Gibson, H. C. Jean, and G. L. Payne,"Nuclear Transition Rates in Ji-Catalyzed p-d Fusion."Phys. Rev. Lett. 66, 1827 (1991).

W. R. Gibbs, J. N. Ginocchio, and N. Auerbach. "PionDouble Charge Exchange: Two-Nucleon Correlations,"Comments Nud. Part. Pins. 20. 141 (1991).

W. R. Gibbs and B. F. Gibson, "Neutron Radius Analysisin the Trhiucleon System from Pion Scattering," Phys.Rev. C43 , 1012 (1991).

W. R. Gibbs and A. C. Hayes, "Determination of theRadius of the ' ' Li Neutron Halo from Pion DoubleCharge Exchange," Phys. Rev. Lett. 67, 1395 (1991).

W. R. Gibbs and A. C. Hayes. "Determination of theRadius of the ' ' Li Neutron Halo from Pion DoubleCharge Exchange," in Proc. of the Conference onIntersections of Particle and Nuclear Physics, Tucson,Arizona. May 24-29. 1991.

B. F. Gibson. "Narrow Structure in Ad Scattering at the ZThreshold (^H States)," Los Alamos National Laboratorydocument LA-UR-91-3891 (1991), in Proc. of theInternational Symposium on Hypenuiclei and StrangeParticle Physics.

B. F. Gibson. "Hypernuclei and Dibaryon Working GroupSummary." Los Alamos National Laboratory documentLA-UR-91-3930 (1991), in Proc. of the IUCF Workshopon Hxperon and Hypernuclear Physics with ProtonBeams, J. J. Szymanski, Ed.

B. F. Gibson, B. C. Pearce, and G. L. Payne. "Reply U>'Comment on Triton Model Calculation Test of the BonnW-Matrix Rank-one Approximation,' " Phys. Rev. C 43.2897(1991).

B. F. Gibson and E. V. Hungerford, 111, "HypernuclearInvestigations with Energetic Pions," Los AlamosNational Laboratory document LA-UR-92-150. in thePILAC Users Group Report, Physics with PI LAC, D. J.Ernst, Ed., p. 64.

B. F. Gibson and E. V. Hungerford. Ill, "HypernuclearInvestigations with Energetic Pions," PILAC TechnicalNote No. 37, January 1992, Los Alamos NationalLaboratory document LA-UR-91-3969.

J. N. Ginocchio, "A B(M1) Sum Rule," Phys. Lett.B265, 6 (1991).

J. N. Ginocchio, "A New Symmetry in CollectiveMotion," in Group Theory and Special Symmetries inNuclear Physics, J. P. Druayer and J. Janecke. Eds.(World Scientific, Singapore, 1992).

J. N. Ginocchio, W. Frank, and P. von Brentano, "MlMatrix Elements and F-Spin Symmetry in Nuclei," Nucl.Phys. A 541, 211 (1992).

J. N. Ginocchio and S. Kuyucak, "Determination of F-Spin Symmetry in Deformed Nuclei," Phys. Rev. C 45.867(1991).

J. N. Ginocchio and A. Leviatan, "Neulron-ProlonCollective Motion I. Energy Surface," Ann. Phys. 216,152(1992).

J. N. Ginocchio, Amiram Leviatan, and Michael W.Kirson, "Is Collective Motion Symmetric in the Neutron-Proton Degrees of Freedom?," in Proc. of the SeventhInternational Symposium on Capture Gamma-RaySpectroscopy and Related Topics, R. W. Hoff. Ed. (AIPConf. Proc. 238. New York, 1991), p. 82.

T. Goldman, " 'Inevitable' Dibaryons." in Proc. of theSecond European Workshop on Hadronic Physics withElectrons Beyond 10 GeV, Dourdan. France. October1990. B. Frois and J-F. Malhiot. Eds.. Nucl. Phys.A 532, 389c (1991).

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T. Goldman, "Chiral Symmetry and Confinement," inElementary Panicles and the Universe (Essays in Honor ofMurray Gell-Mann), J. H. Schwarz, Ed. (CambridgeUniversity Press, New York, 1991), p. 41.

T. Goldman, "An Inevitable Dibaryon," presented at theFourth Conference on the Intersections Between Particleand Nuclear Physics, Tucson, Arizona, May 24-29. ! 991.

T. Goldman. J. A. Henderson, and A. W. Thomas,"Substructure Effect on pco Mixing in Charge SymmetryViolation," Los Alamos National Laboratory documentLA-UR-91-2010 and ADP-91-157/T97 [accepted forpublication in Modern Physics Letters A (1992)].

T. Goldman. J. A. Henderson, and A. W. Thomas. "ANew Perspective on the pro Contribution to ChargeSymmetrv in the NN Force," Few Body Systems 12, 123(1992).

T. Goldman. J. Perez-Mercader, F. Cooper, and M. M.Nieto, "The Dark Matter Problem and Quantum Gravity,"Phys. Lett. B 281. 219 (1992).

P. Herczeg, "CP-Violation in Extensions of the StandardModel and Time-Reversal Violation in Low EnergyNuclear Processes." in Progress in Nuclear Physics. W-Y.Pauchy Hwang, S-C. Lee, C-E. Lee, and D. J. Ernst, Eds.(North Holland, 1991), p. 171.

P. Herczeg, "The Neutrinos in Muon Decay," Los AlamosNational Laboratory document LA-UR-91-3461 (to bepublished in Zeitschrift fur Physik C, 1992).

P. Herczeg, "Theoretical Aspects of Searches for NewInteractions Using Oriented Nuclei," Los Alamos NationalLaboratory document LA-UR-92-577 (to appear inHyperfine Interactions, 1992).

P. Herczeg. "The Decays r| —» jiev e and r| —> 7tj.tvu," in

Proc. of the Fourth Conference on the IntersectionsBetween Particle and Nuclear Physics, Tucson. Arizona.May 24-29. 1991. W. T. H. Van Oers. Ed. {AIP Conf.Proc. 243, New York. 1992), p. 654.

P. Herczeg and R. N. Mohapatra. "Muonium toAntimuonium Conversion and the Decay | i + —> e + v e v u

in Left-Right Symmetric Models." in Proc. of theParticles and Fields VI. 1991. D. Axen. D. Bryinan. andM. Comyn. Eds. (World Scientific. 1992). p. 572.

Theory

P. Herczeg, "Some Rare ^-Decays - Overvi w of theTheory," in the PILAC Users Group Report. Physics withPI LAC. D. J. Ernst. Ed.. Los Alamos NationalLaboratory document LA-L'R-92-150. p. 126.

W. B. Kaufmann and W. R. Gibbs. "Isospin-SymmetryBreaking in the Pion-Nucleon System," Los AlamosNational Laboratory document LA-UR-91-310 (to bepublished in Annals of Physics).

A. Leviatan and J. N. Ginocchio, "Proton-Neutron Modesin Non-Axial Nuclei," Phys. Lett. B 267. 7 (1991).

K. Maltman, T. Goldman, and G. J. Stephenson, Jr.,"Charge Symmetry Breaking in the A = 3 System andElectromagnetic Penguins (of the Second Kind)." Nucl.Phys. A 530, 539 (1991).

R. Schiavilla, R. B. Wiringa, and J. Carlson, "DeltaContributions to A = 4 Weak and ElectromagneticCapture" (submitted to Physical Review C).

R. R. Silbar, "Scattering Amplitudes to All Orders inMeson Exchange," in From Fundamental Fields toNuclear Phenomena, Boulder, Colorado (World Scientific.Singapore, 1991).

R. R. Silbar and H. W. Egdorf. "Object-OrientedInventories: Comparison of Implementations in KEE andCLOS." Los Alamos National Laboratory documentLA-UR-90-3692, in Proc. of the Society of ComputerSimulation, 1991.

G. J. Stephenson. Jr., K. Maltman, and T. Goldman."QCD Corrections to QED and Isospin Breaking in theBaryon Spectrum and Vector Meson Mixing." Phvs. Rev.D43, 860(1991).

Fan Wang, Guang-han Wu, Li-Jian Teng. and T.Goldman, "Quark Delocalization. Color Screening, andNuclear intermediate Range Attraction," Los AlamosNational Laboratory document LA-UR-91-2152(submitted to Physical Review Letters. 1991).

H. T. Williams and R. R. Siibar. "Automated AngularMomentum Recoupling Algebra" (to be published in theJournal of Computational Physics. March 1992).

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ResearchTheory

Invited Presentations

This section does not include seminars presented,eivher external or internal, nor ordinary contributions toconferences or meetings.

J. Carlson, "Monte Carlo Approaches to Light Nuclei:Structure and Electron Scattering," presented at theSymposium in Honor of Akiw Arima, Santa Fe, NewMexico, 1990.

J. Ca.lson, "Three-Nucleon Interactions in A = 4 & 5Systems," presented at the Workshop on the NuclearHamiltonian and Electromagnetic Current in the 90's,Argonne National Laboratory, August 1991.

J. Carlson and K. E. Schmidt, "Monte Carlo Approachesto Effective Field Theories," presented at Recent Progressin Manx-Bod\ Theories VII, Minneapolis, Minnesota,August 1991.

J. L. Friar, "Few-Nucleon Systems." five invited lecturesat the Summer Nuclear Institute at TRIUMF, Vancouver,British Columbia, July-August 1991.

J. L. Friar, "p-d Capture Reactions in MuonicMoleciles," presented at the XHIlh European Conferenceon Few-Body Problems in Physics, Marciana Marina,lsola d'Elba, Italy, September 1991.

J. L. Friar, "n-d and p-d Capture Reactions at ExtremelyLow Energies," presented at the Workshop on the NuclearHamiltonian and the Electromagnetic Current for the 90's,Argonne National Laboratory (August 1991).

J. L. Friar, "New Approaches for Bound and ScatteringStates," convener's report at the XHIth EuropeanConference on Few-Body Problems in Physics, MarcianaMarina, Isola d'Elba, Italy, September 1991.

W. R. Gibbs, "Determining Neutron Radii with Pions,"presented at Pions in Nuclei, Penyscola. Spain, June1991.

W. R. Gibbs and A. C. Hayes, "Determination of theRadius of the ' ' L i Neutron Halo from Pion DoubleCharge Exchange." presented at the Fourth Conference onthe Intersections Between Particle and Nuclear Physics,Tucson, Arizona, May 24-29, 1991.

B F. Gibson, "Narrow Structure in Ad Scattering at the SThreshold [\li States)," presented at the InternationalSymposium on Hypernuclei and Strange Particle Physics.Shimoda, Japan, December 1991.

B. F. Gibson, "Hypernuclei and Dibaryon Working GroupSummary," presented at the 1UCF Workshop on Hyperonand Hypernuclear Physics with Proton Beams,Bloomington, Indiana, November 1991.

J. N. Ginocchio, "A New Symmetry in CollectiveMotion," presented at the International Symposium onGroup Theory and Special Symmetries in NuclearPhysics, Ann Arbor, Michigan, September 1991.

J. N. Ginocchio, Amiram Leviatan, and Michael W.Kirson, "Is Collective Motion Symmetric in the Neutron-Proton Degrees of Freedom?," presented at the SeventhInternational Symposium on Capture Gamma-RaySpectroscopy and Related Topics, October 1990.

T. Goidman, " 'Inevitable' Dibaryons," presented at theSecond European Workshop on Hadronic Physics withElectrons Beyond 10 GeV, Dourdan, France, October1990.

T. Goldman, "An Inevitable Dibaryon," presented at the4th Conference on the Intersections Between Particle andNuclear Physics, Tucson, Arizona, May 24-29, 1991.

P. Herczeg, "Selected Topics in Muon Decay," presentedat the Workshop on the Future of Muon Physics,Heidelberg, Germany, May 1991.

P. Herczeg, "The Nature of Neutrinos from Muon Decay."presented at the Workshop on Frontiers of EiectroweakPhysics, Santa Fe, New Mexico, August 1991.

P. Herczeg, "Light Meson Decays al PILAC,"presentation of the report of the PILAC Working Groupon light meson decays, PILAC Users Group Meeting.LAMPF. Los Alamos, February 1991, and at PILACUsers Group Meeting, Washington. DC, April 1991.

P. Herczeg, "The Decays r\ —> neve and V) -> 7t|iVu."presented at the Fourth Conference on the IntersectionsBetween Particle and Nuclear Physics. Tucson, Arizona,May 24-29. 1991.

106

Research

P. Herczeg. "Muonium to Aniimuonium Conversion andthe Decay | i + —> e + v e v u in Left-Right SymmetricModels." presented at the Proc. of Particles and Fields '91Conference of the APS, Vancouver. British Columbia,August 1991.

P. Herczeg, "Theoretical Aspects of Searches for NewInteractions Using Oriented Nuclei." presented at theSecond International Conference on On-Line NuclearOrientation and Related Topics, Oak Ridge, Tennessee,October 16-19, 1991.

Theory

R. R. Silbar, "Scattering Amplitudes to All Orders inMeson Exchange," presented at From Fundamental Fieldsto Nuclear Phenomena, Boulder, Colorado, 1991.

R. R. Silbar, "Hadron Scattering Amplitudes in the Limitof a Large Number of Colors," colloquium given at theCatholic University of America, September 1991.

R. R. Silbar and H. W. Egdorf, "Object-OrientedInventories: Comparison of Implementations in KEE andCLOS," presented at the Society of Computer SimulationMeeting, Anaheim, California, January 1991.

107

ResearchPublications

MP-Division Publications

D. M. Aide. H. W. Baer, T. A. Carey, G. T. Garvey, A.Klein, C. Lee, M. J. Leitch, J. W. Lillberg, P. L.McGaughey, C. S. Mishra, J. M. Moss, J. C. Peng, C.N. Brown, W. E. Cooper, Y. B. Hsiung, M. R. Adams,R. Guo, D. M. Kaplan, R. L. McCarthy, G. Danner, M.J. Wang, M. L. Barlett, and G. W. Hoffman, "NuclearDependence of the Production of T Resonances at800 GeV," Phys. Rev. Lett. 66, 2285 (1991).

D. E. Alexandreas, R. C. Allen, S. D. Biller, R. S.Delay, G. M. Dion, X-Q. Lu, P. R. Vishwanath, G. B.Yodh, D. Berley, C. Y. Chang, B. L. Dingus, J. A.Goodman, T. J. Haines, S. Gupta, D. A. Krakauer, M. J.Stark, R. L. Talaga, R. L. Burman, K. Butterfield, R.Cady, C. M. Hoffman, J. Lloyd-Evans, D. E. Nagle, M.E. Potter, V. D. Sandberg, C. Sinnis, S. Stanislaus, T.N. Thompson, C. A. Wilkinson, W. Zhang, and R. W.Ellsworth, "The CYGNUS Extensive Air-ShowerE x p e r i m e n t , " Nucl. lustrum. Methods A 3 1 1 , 350

(1992).

D. E. Alexandreas, D. Berley, S. Biller, R. L. Burman, D.R. Cady, C. Y. Chang. B. L. Dingus, C. L. Dion, G. M.Dion, R. W. Ellsworth, S. J. Freedman, B. K. Fujikawa,J. A. Goodman, T. J. Haines, C. M. Hoffman. D. A.Krakauer. P. W. Kwok, X-Q. Lu, D. E. Nagle, M. Potter,V. D. Sandberg, C. Sinnis, M. J. Stark. P. R.Vishwanath, G. B. Yodh, and W. P. Zhang, "A Search ofthe Northern Sky for Ultra-High-Energy Point Sources,"Astrophys. J. 383, L53 (1991).

D. E. Alexandreas, D. Berley, S. Biller, R. L. Burman, D.R. Cady, C. Y. Chang, B. L. Dingus. C. Dion, G. M.

Dion, R. W. Ellsworth, S. J. Freedman, B. K. Fujikawa,J. A. Goodman, T. J. Haines, C. M. Hoffman, D. A.Krakauer, P. W. Kwok, X-Q. Lu, D. E. Nagle, M. Potter,V. D. Sandberg, C. Sinnis, M. J. Stark, D. Williams, G.B. Yodh, and W. P. Zhang, "Search for UHE CosmicRays from the Crab Nebula/Pulsar," in 22nd InternationalCosmic Ray Conference, Dublin, Ireland, August 11 -23,1991 (Reprint, Ltd., Dublin, Ireland), Vol. 1, p. 216.

D. E. Alexandreas, D. Berley, S. Biller, R. L. Burman, D.R. Cady, C. Y. Chang, B. L. Dingus, C. Dion, G. M.Dion, R. W. Ellsworth, S. J. Freedman, B. K. Fujikawa,J. A. Goodman, T. J. Haines, C. M. Hoffman. D. A.Krakauer, P. W. Kwok, X-Q. Lu, D. E. Nagle, M. Potter,V. D. Sandberg, C. Sinnis, M. J. Stark, T. Tsutsumi, D.Williams, D. D. Weeks, G. B. Yodh, and W. P. Zhang,"Characteristics of 'Anomalous Muon' Events Associatedwith Hercules X-l." in 22nd International Cosmic RayConference, Dublin, Ireland, August 11-23, 1991(Reprint, Ltd., Dublin, Ireland), Vol. 1. p. 249.

D. E. Alexandreas. D. Berley, S. Biller, R. L. Burman, D.R. Cady, C. Y. Chang, B. L. Dingus, C. Dion, G. M.Dion, R. W. Ellsworth, S. J. Freedman, B. K. Fujikawa,J. A. Goodman, T. J. Haines, C. M. Hoffman, D. A.Krakauer, P. W. Kwok, X-Q. Lu, D. E. Nagle, M. Potter.V. D. Sandberg, C. Sinnis, M. J. Stark, T. Tsutsumi, D.Williams. D. D. Weeks, G. B. Yodh, and W. P. Zhang,"Search for Daily Emission of Ultra High Energy AirShowers from Point Sources with the CYGNUSExperiment," in 22nd International Cosmic RayConference, Dublin, Ireland. August 11-23, 1991(Reprint, Ltd.. Dublin, Ireland). Vol. 1, p. 301.

108

Research

D. E. Alexandreas, D. Berley. S. Biller, R. L. Burman, D.R. Cady. C. Y. Chang. B. L. Dingus, C. Dion, G. M.Dion, R. W. Ellsworth, S. J. Freedman. B. K. Fujikawa.J. A. Goodman. T. J. Haines. C. M. Hoffman, D. A.Krakauer, P. W. Kwok. X-Q. Lu. D. E. Nagle. M. Potter,V. D. Sandberg. C. Sinnis, M. ) . Stark, T. Tsutsumi. D.Williams. D. D. Weeks, G. B. Yodh, and W. P. Zhang,"Search for Pulsed UHE Emission from 4U0115+63," in22nd International Cosmic Ray Conference. Dublin,Ireland. August 11-23, 1991 (Reprint, Ltd., Dublin,Ireland), Vol. l .p . 352.

D. E. Alexandreas. D. Berley, S. Biller, R. L. Burman. D.R. Cady. C. Y. Chang. B. L. Dingus, C. Dion. G. M.Dion. R. W. Ellsworth, S. J. Freedman, B. K. Fujikawa.J. A. Goodman. T. J. Haines, C. M. Hoffman, D. A.Krakauer. P. W. Kwok, X-Q. Lu, D. E. Nagle, M. Potter,V. D. Sandberg, C. Sinnis. M. J. Stark, T. Tsutsumi, D.Williams. D. D. Weeks. G. B. Yodh. and W. P. Zhang,"A Search for Steady Emission from Ultra High EnergySources," in 22nd International Cosmic Ray Conference,Dublin, Ireland, August 11-23. 1991 (Reprint, Ltd.,Dublin, Ireland), Vol. 1, p. 436.

D. E. Alexandreas, D. Berley, S. Biller. R. L. Burman, D.R. Cady, C. Y. Chang, B. L. Dingus. C. Dion, G. M.Dion. R. W. Ellsworth, S. J. Freedman. B. K. Fujikawa,J. A. Goodman. T. J. Haines, C. M. Hoffman, D. A.Krakauer, P. W. Kwok, X-Q. Lu, D. E. Nagle, M. Potter,V. D. Sandberg, C. Sinnis, M. J. Stark, T. Tsutsumi, D.Williams. D. D. Weeks, G. B. Yodh. and W. P. Zhang."Angular Resolution of the CYGNUS EAS Array fromthe Shadows of the Moon and the Sun." in 22ndInternational Cosmic Ray Conference, Dublin, Ireland,August 11-23, 1991 (Reprint, Ltd., Dublin, Ireland),Vol. 2, p. 672.

D. E. Alexandreas, D. Berley, S. Biller, R. L. Burman, D.R. Cady, M. Cavalli-Sforza, C. Y. Chang, D. G. Coyne,B. L. Dingus, C. L. Dion, G. M. Dion, D. E. Dorfan. R.W. Ellsworth. S. J. Freedman. B. K. Fujikawa, J. A.Goodman, T. J. Haines, C. M Hoffman, D. A. Krakauer,P. W. Kwok, X-Q. Lu, D. E. Nagle, M. Potter, V. D.Sandberg, C. Sinnis, M. J. Stark, T. Tsutsumi, D. A.Williams, D. H. Williams, D. D. Weeks, G. B. Yodh,and W. P. Zhang, "Studies on Improving the AngularResolution of the CYGNUS Array," in 22nd InternationalCosmic Ray Conference, Dublin. Ireland, August 11-23,1991 (Reprint, Ltd., Dublin, Ireland), Vol. 2. p. 676.

Publications

D. E. Alexandreas, D. Berley. S. Biiler. R. L. Burman. D.R. Cady, C. Y. Chang, B. L. Dingus. C. Dion. G. M.Dion, R. W. Ellsworth, S. J. Freedman, B. K. Fujikawa.J. A. Goodman, T. J. Haines, C. M. Hoffman. D. A.Krakauer. P. W. Kwok, X-Q. Lu. D. E. Nagle, M. Potter.V. D. Sandberg, C. Sinnis. M. J. Stark. D. Williams. G.B. Yodh. and W. P. Zhang. "Detailed Simulation of theCYGNUS Array's Response to Extensive Air Showers,"in 22nd International Cosmic Ray Conference, Dublin.Ireland, August 11-23. 1991 (Reprint, Ltd.. Dublin.Ireland). Vol. 4, p. 504.

R. C. Allen, R. L. Burman, D. R. Cady, C. Y. Chang,R. S. DeLay, R. W. Ellsworth. S. Gupta. J. A.Goodman, T. J. Haines, D. A. Krakauer. J. Lloyd-Evans,X-Q. Lu, D. E. Nagle, M. E. Potter, V. D. Sandberg. A.J. Sena, R. L. Talaga, T. N. Thompson, and G. B. Yodh."Use of Neutrino Detector for Muon Identification by theCYGNUS Air-Shower Array," Nucl. lustrum. MethodsA 311, 368 (1992).

R. C. Allen, H. H. Chen, P. J. Doe, R. Hausammann,W. P. Lee, H. J. Mahler. M. E. Potter, X-Q. Lu. K. C.Wang. T. J. Bowles, R. L. Bunnan, R. D. Carlini, D. R.F. Cochran, J. S. Frank, E. Piasetzky, V. D. Sandberg,D. A. Krakauer, and R. L. Talaga, "Experimental Boundon the Charge Radius of the Electron Neutrino," Phys.Rev. D 4 3 , RI (1991).

P. Arendl, N. Elliott, K. Hubbard, M. Maley. J. YatesCoulter, B. Bennett, J. Martin, R. Dye, A. Rollett, and T.Schofield. "Fabrication and Characterization of Thallim-Barium-Calcium-Copper-Oxide Superconducting Films onLanthanum Aluminate Substrates," Los Alamos NationalLaboratory document LA-UR-91-2656.

M. S. Atiya, 1-H. Chiang, J. S. Frank, J. S. Haggerty.M. M. Ito, T. F. Cycia, K. K. Li, L. S. Littenberg, A.Stevens, R. C. Strand, W. C. Louis. D. S. Akerib, D. R.Marlow, P. D. Meyers, M. A. Selen, F. C. Shoemaker,A. J. S. Smith, G. Azuelos. E. W. Blackmore. D. A.Bryman. L. Felawka, P. Kitching. Y. Kuno, j . A.Macdonald, T. Numao, P. Padley, J-M. Poutissou, R.Poutissou, and J. Roy, "Upper Limit on the BranchingRatio for the Decay Jt° —» vv." Phys. Rev. Lett. 66 .2189(1991).

Helmut W. Baer, "Single and Double Charge Exchange atLow Pion Energies." Los Alamos National Laboratory

109


document LA-UR-91-2827 (invited talk given at TheInternational Workshop on Pious in Nuclei, June 3-8,1991, Pensicola, Spain).

M. L. Barlett, R. W. Fergerson, G. W. Hoffmann, J. A.Marshall. L. Ray, J. F. Amann, B. E. Bonner, J. B.McClelland, "Inclusive Quasielastic Spin Observables forp> + 2H. 12C at 500 MeV." Phys. Lett. B 264, 21(1991).

Johann Bartel, M. B. Johnson, Mano Singham, andWilhelm Stocker, "Microscopic Coupled-ChannelDescription of Pion Inelastic Scattering from RotationalNuclei," Los Alamos National Laboratory documentLA-UR-92-973 (submitted to Nuclear Physics, March1992).

Johann Bartel, M. B. Johnson. Mano Singham, andWilhelm Stocker. "Pion Inelastic Scattering and theNeutron Density in ' ^ s ^ " LO S Alamos NationalLaboratory document LA-UR-92-972 (submitted toPhysics Letters, March 1992).

M. Beddo, G. Burleson, J. A. Faucett, S. Gardiner, G.Kyle, R. Garnett, D. P. Grosnick, D. Hill, K. F.Johnson, D. Lopiano, Y. Ohashi, T. Shima, H. Spinka,R. Stanek, D. Underwood, A. Yokosawa, G. Glass, R.Kenefick, S. Nath, L. Northcliffe. J. J. Jarmer, S.Penttila, R. H. Jeppesen, G. Tripard, M. Devereux, and P.Kroll, "Measurements of AOL (np) between 500 and800 MeV," Phys. Leu. B 258, 24 (1991).

D. Berley. C. L. Dion, J. A. Goodman, T. J. Haines, P.W. Kwok, M. J. Stark, R. C. Svoboda, H. Razani, H.Ferguson, C. M. Hoffman, E. Horch, C. Sinnis, R. W.Ellsworth, R. S. Delay, X-Q. Lu, and G. B. Yodh,"JASA: Initial Results from a Prototype Water-CerenkovAir-Shower Detector," in 22nd International Cosmic RayConference, Dublin, Ireland, August 11-23, 1991(Reprint, Ltd., Dublin, Ireland), Vol. 2, p. 680.

R. Bilger, B. M. Barnett, H. Clement, S. Krell, G. J.Wagner, J. Jaki, C. Joram, T. Kirchner, W. Kluge, MMetzler, R. Wieser, C. L. Morris, and D. Renker, "FirstDCX-Measurements with LEPS at 50 MeV" (submittedto the Proceedings of the International Workshop onPions in Nuclei, Peniscola, Spain, June 3-8, 1991).

B. Blind, "Injection Lines for PILAC," P1LAC TechnicalNote No. J5, Los Alamos National Laboratory documentLA-UR-91-683 (February 12, 1991).

B. Blind, "PILAC Reference-Design Injection Line,"PILAC Technical Note No. 16, Los Alamos NationalLaboratory document LA-UR-91-684 (February 15, 1991).

J. D. Bowman, J. E. Bush, P. P. J. Delheij, C. R. Gould,D. G. Haase, J. N. Knudson, G. E. Mitchell, S. Penttila,H. Postma, N. R. Robertson, S. J. Seestrom, J. J.Szymanski, S. Yoo, V. W. Yuan, and X. Zhu, "SignCorrelations and Parity Nonconservation for NeutronResonances in "^-Th," Los Alamos National Laboratorydocument LA-UR-9I-1253 (submitted to Physical ReviewLetters, April 1991).

J. D. Bowman, G. T. Garvey, C. R. Gould, A. C. Hayes,and M. B. Johnson, "Parity Violation in the CompoundNucleus: The Role of Distant States," Phys. Rev. Lett.68, 780 (1992).

M. L. Brooks, B. D. Bassalleck, R. A. Reeder, D. M.Lee, J. A. McGill. M. E. Schillaci, R. A. Ristinen, andW. R. Smythe, "Neutron Induced Pion Production on C,Al, Cu, and W at 200-600 MeV," Phys. Rev. C45.2343(1992).

Howard C Bryant and Chris H. Greene, "New Light on aDark Ion," in Physics 'tews in 1991, American Instituteof Physics, 15(1991).

R. L. Burman, R. C. Allen, T. J. Bowles. R. D. Carlini,H. H. Chen, D. Cochran. P. J. Doe. J. S. Frank. R.Hausammann, D. A. Krakauer, W. P. Lee. X-Q. Lu. H. J.Mahler, E. Piasetzky, M. E. Potter, V. D. Sandberg. R.L. Talaga, and K. C. Wang. "Experimental Study ofNeutrino Properties," in The Vancauvi - Meeting -Particles and Fields '91, Vancouver, Brili h Columbia,Canada, August 18-22, 199), David Axen, DouglasBryman, and Martin Comyn, Eds. (World Scientific,Singapore, 1992), p. 946.

P. Busch and G. Swain, "Summary of 805-MHz CavityStudies," PILAC Technical Note No. 18. Los AlamosNational Laboratory document LA-UR-91-1140 (April 1.1991).

110

Research

H. Butler, Z. Li, and H. A. Thiessen, "Using MOTER toDesign PILAC," in Conference Record of the 1991 IEEEParticle Accelerator Conference, San Francisco,California, May 6-9, 1991, 91CH3038-7(l), pp. 281-283.

C. M. Chen. D. J. Ernst, and M. B. Johnson,"Microscopic Approach to Pion-Nucleus Dynamics," LosAlamos National Laboratory document LA-UR-92-1589(submitted to Physical Review C, 1992).

M. D. Cooper. "Experimental Prospects for ObservingFamily-Number Violating Decays," in Proc. of theSecond International Symposium on Particles, Strings andCosmology, Boston, Mrssachussetts. March 25-30, 1991,Pran Nath and Stephen Reucroft, Eds. (World Scientific,1992), p. 186.

R. A. DeHaven, "PILAC Cavity Coupling Estimates,"PILAC Technical Note No. 22, Los Alamos NationalLaboratory document LA-UR-91-2606 (July 1991).

J. F. Dicello, M. E. Schillaci, and L.-C. Liu, "CrossSections for Pion, Proton, and Heavy-Ion Production from800-MeV Protons Incident Upon Aluminum and Silicon,"Nucl. lustrum. Methods B 45, 135 (1990).

G. H. Eaton, "Recommendations for the New MuonFacilities with the LAMPF PILAC Upgrade," PILACTechnical Note No. 29, Los Alamos National Laboratorydocument LA-UR-91-2723 (August 16, 1991).

G. H. Eaton, "Recommendations for a Pulsed MuonFacility Associated with the PSR Upgrade," PILACTechnical Note No. 30, Los Alamos National Laboratorydocument LA-UR-91-2727 (August 20, 1991).

G. H. Eaton, "The PSR and PILAC Muon Facilities atLAMPF," PILAC Technical Note No. 31, Los AlamosNational Laboratory document LA-UR-91-2728(August 20, 1991).

B. S. Flanders. J. J. Kelly, H. Seifert, D. Lopiano, B.Aas. A. Azizi, G. Igo, G. Weston, C. Whilten, A. Wong,M. V. Hynes, J. McClelland, W. Bertozzi, J. M. Finn, C.E. Hyde-Wright, R. W. Lourie, B. E. Norum, P. Uliner,and B. L. Berman, "Empirical Density-DependentEffective Interaction for Nucleon-Nucleus Scattering at500 MeV," Phys. Rev. C 43, 2103 (1991).

Publications

S. J. Freedman, B. K. Fujikawa. D. A. Krakauer, S.Barwick, R. S. Delay, X-Q. Lu, G. B. Yodh, T. J.O'Neill, O. T. Turner, A. Zych M. Cavalli-Sforza, D. G.Coyne. D. E. Dorfan. D. A. Williams. R. C. Lamb, R.L. Burman, C. M. Hoffman. E. C. Milner, D. E. Nagle,M. E. Potter. V. Sandberg, C. Sinnis, D. H. White, Z.Zhang, R. Svoboda, C. Y. Chang, J. A. Goodman, T. J.Haines, P-W. Kwok, R. W. Ellsworth, A. I. Mincer, P.Nemethy, J. Sculli, and D. D. Weeks, "A Detector for 1-1,000-TeV Cosmic Rays," (The MILAGRO Deteuor)Proposal (January 1991).

G. T. Garvey, "The A Dependence of DileptonProduction," Nucl. Physics A 532, 119c (1991).

G. T. Garvey, "Recent Developments in NeutrinoPhysics," Nucl. Phys. A 546. 369c (1992).

B. F. Gibson, W. R. Gibbs, and M. B. Johnson, Eds.,LAMPF Workshop on <7i,K) Physics, AIP Conf. Proc.224 (AIP, 1991).

G. Glass, T. S. Bhatia, J. C. Hiebert, R. A. Kenefick, S.Nath, L. C. Northcliffe, W. B. Tippens, D. B. Barlow, J.J. Jarmer, J. E. Simmons, R. H. Jeppesen, and G. E.Tripard, "Measurement of Spin-Correlation ParametersA L L and A S L in p-p Elastic Scattering from 500 to800 MeV," Phys. Rev. C 45, 35 (1992).

J. J. Gorgen, "Analyzing Power Measurements for the(ji+,rc°) Reaction on a Polarized l 3 C Target," Ph.D.thesis, Arizona State University, Los Alamos NationalLaboratory report LA-12093-T (1991).

J. J. Gorgen, J. R. Comfort, J. R. Tinsley, T. Averett, J.DeKorse. B. Franklin. B. G. Ritchie, G. S. Kyle, A.Klein, B. Berman, G. R. Burleson, K. Cranston. J. A.Faucett, J. J. Jarmer, J. N. Knudson, S. Penttila, N.Tanaka, B. Brinkmoller. D. Dehnhard, Y. F. Yen. S.H0ibraten, H. Breuer, B. S. Flanders, M. A. Khandaker,D. L. Naples, D. Zhang, M. L. Barlett, G. W. Hoffmann,and M. Purcell, "Analyzing Powers for Pion ChargeExchange on Polarized 13C," Phys. Rev. Lett. 66. 2193(1991).

P. Grand, "Preliminary Analysis of a Lithium Lens forPILAC," PILAC Technical Note No. 8. Los AlamosNational Laboratory document LA-UR-90-4425(November 1990).

111


P. Grand, "Visit to CEBAF." PILAC Technical Note No.11. Los Alamos National Laboratory document LA-UR-91-606 (January 16. 1991).

P. Grand. "PILAC Pulsed Magnet Line," PILACTechnical Note No. 35. Los Alamos National Laboratorydocument LA-UR-91-3415 (October 29. 1991).

E. R. Gray. "Multicell Cavity Tuning." PILAC TechnicalNote No. 21. Los Alamos National Laboratory documentLA-UR-91-969 (March 19. 1991).

Andrew A. Greene. "The Spin Response of "*^Ca at 500and 580 MeV." Ph.D. thesis. Rutgers University, LosAlamos National Laboratory report LA-12226-T(December 1991).

E. Giilmez. S. Beedoe. T. Jaroszewica. A. G. Ling. C. A.Whitten. Jr., M. W. McNaughton, J. R. Santana, D. L.Adams. V. R. Cupps. A. J. Simon. M. L. Barlett, K. H.McNaughton. and P. J. Riley. "Absolute DifferentialCross-Section Measurements for Proton-Deuteron ElasticScattering at 641.3 and 792.7 MeV," Phys. Rev. C 43.2067(1991).

E. Giilmez. D. L. Adams. S. Beedoe, M. Bleszynski. I.Bystricky. V. Ghazikhanian, G. Igo, T. Jaroszewicz. A.G. Ling. M. Nasser. M. W. McNaughton, S. Penttila, G.Glass. G. Kahrimanis. W. F. Kielhorn. K. H.McNaughlon. P. J. Riley. S. Sen. and D. Wolf. "ElasticScattering of N. L. and S-Type Polarized 794-MeVProtons from an ND3 Target Polarized in the S-L Plane."Pins. Rev. C 45. 22 (1992).

R. Quick. "Observation of Field-Induced Structure andThreshold Shifts in the H" Photodetachment Spectrum"(submitted to Physical Review Letters. 1992).

P. G. Harris. H. C. Bryant. A. H. Mohagheghi. R. A.Reeder, C. Y. Tang. J. B. Donahue, and C. R. Quick,"Observations of Doubly Excited Resonances in the H~Ion," Phys. Rev. A 42, 6443 (1990).

H. L. Heinisch, M. L. Hamilton. W. F. Sommer. and P.D. Ferguson, "Tensile Property Changes of MetalsIrradiated to Low Doses with Fission, Fusion, andSpallalion Neutrons," Los Alamos National Laboratorydocument LA-UR-91-1270. presented at the FifthInternational Conference on Fusion Reactor Materials,Clearwater, Florida. November 1991 (to be published inthe Journal of Nuclear Materials. 1992).

A. P. Heinson, J. Horvath, C. Mathiazhagan, W. R.Molzon, K. Arisaka, R. D. Cousins, T. Kaarsberg, J.Konigsberg, P. Rubin. W. E. Slater. D. L. Wagner.W. W. Kinnison, D. M. Lee, R. J. McKee. E. C.Milner. G. H. Sanders. H. J. Ziock, P. Knibbe, J.Urheim. K. A. Biery, M. V. Diwan, G. M. uvvin. K.Lang. J. Margulies. D. A. Ouimette. A. Schwartz. S. G.Wojcicki, L. B. Auerbach, J. Belz. P. Buchholz. V. L.Highland, W. K. McFarlane. M. Sivertz, J. L. Ritchie. A.Yamashita. M. D. Chapman. M. D. Eckhause, J. F.Ginkel. A. D. Hancock, J. R. Kane. C. J. Kenney. Y.Kuang, W-F. Vulcan, R. E. Welsh, R. J. Whyley. andR. G. Winter. "Higher-Statistics Measurement of theBranching Ratio for the Decay Kj —> (j.jj.," Phys. Rev.D 4 4 , RI-R5 (1991).

E. U. Haebel and J. McGill. "Calculating the StandingWave Ratio of a Passive. Lossfree Microwave JunctionUsing Superfish." PILAC Technical Note No. 25. LosAlamos National Laboratory document LA-UR-91-1507(April 1991).

M. Halka. H. C. Bryant. E. P. Mackerrow. W. Miller. A.H. Mohagheghi. C. Y. Tang. S. Cohen. J. B. Donahue.A. Hsu. C. R. Quick. J. Tiee. and K. Rozsa."Observation of the Partial Decay into H()(n' = 2) byExcited H~ Near the n = 3 and 4 Thresholds." Phys. Rev.A 44, 6127 (1991).

M. Halka. P. G. Harris. A. H. Mohagheghi. R. A.Reeder. C. Y. Tang. H. C. Bryant. J. B. Donahue, and C.

N. M. Hintz. X. H. Yang. M. Gazzaly, S. J. Seestum-Morris. C. L. Morris. D. C. Cook. A. M. Mack. J. S.McDonald. D. S. Oakley. C. F. Moore. M. Lynker. andJ. D. Zumbro. "Determination of Neutron and ProtonMultipole Matrix Elements in 20Hpj, from JJ- ancj n+Scattering at 180 MeV," University of MinnesotaSupercomputer Institute Research Report. UMSI 91/127.(1991).

C. M. Hoffman. "Summary - Neutrinos and Non-accelerator Physics." in Proc. of the IVth Conference onthe Intersections between Particle and Nuclear Physics.Tucson, Arizona. May 23-29. 1991. Willem T. H. vanOers. Ed. (AlP Conf. Proc. 243. American Institute ofPhysics. New York. 1992). p. 1061.

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Research

S. Hoibraten, S. Gilad, W. J. Burger. R. P. Redwine, E.Piasetzky, H. W. Baer. J. D. Bowman. F. H. Cverna, F.Irom, M. J. Lcitch. J. N. Knudson. S. A. Wood, and S.H. Rokni, "Coincidence Measurements of the (Jt+,7i"p)Reactions at Tn+ = 165 MeV," Pins. Rev. C 4 3 , 1255(1991).

M. B. Johnson. E. Osel, H. Sarafian, E. R. Siciliano. andM. Vicente-Vacas, "Meson Exchange Currents in PionDouble Charge Exchange," Phys. Rev. C 44. 2480(1991).

Publications

Interaction for l6O(p,p') at Ep = 318 MeV." Phys. Rev.C 4 3 , 1272 (1991).

L. S. Kisslinger and M. B. Johnson. "Light-Front ShellModel: EMC Effect," Pins. Lett. B 259, 416 (1991).

J. N. Knudson. C. L. Morris, J. D. Bowman, W. C.Sailor. S. J. Seestrom. I. Supek. M. E. Sadler, and L. D.Isenhower, "Search for Neutral Pions from theSpontaneous Fission of 252Cf," Phys. Rev. C44 , 2869(1991).

M. B. Johnson, J. D. Bowman, and S. H. Yoo. "Theoryof Parity Nonconservation in Compound-Nucleon States,"Phys. Rev. Lett. 67, 310 (1991).

M. B. Johnson, "Short-Range NA and NN Correlations inPion Double Charge Exchange." in Progress in NuclearPhysics, W.-Y. P. Hwang, S. H. Lee. C-E. Lee, and D. J.Ernst. Eds. (North Holland, 1991), p. 329.

M. B. Johnson. "Light-Front Nuclear Shell Model," inQuark-Gluon Structure of Hadrons and Nuclei, L. S.Kisslinger and X. Qiu, Eds. (International AcademicPublishers. 1991), p. 67.

M. B. Johnson and David Ernst. "Meson-NucleusDynamics," Los Alamos National Laboratory documentLA-UR-92-230 (to be published in Annals of Physics,1992).

M. K. Jones. R. D. Ransome, V. R. Cupps. R. W.Fergerson, C. L. Morris, J. A. McGill, J. D. Zumbro, J.R. Comfort, B. G. Ritchie, J. R. Tinsley, P. C. Gugelot,and C. Fred Moore, "Pion Absorption Above the A( 1232)Resonance." Los Alamos National Laboratory documentLA-UR-91-2608 (submitted to Physical Review Letters,1991).

M. K. Jones, R. D. Ransome, D. Clayton. K. Pujara, B.G. Ritchie. C. L. Morris, .1. A. McGill, D. L. Watson,C. Fred Moore. I. Brown, and P. Campbell. "EnergyDependence of the Total 12C(7t+.2p) Cross Section."Phys. Lett. B 278. 419 (1992).

J. J. Kelly. A. E. Feldman, B. S. Flanders, H. Seifert, D.Lopiano, B. Aas. A. Azizi, G. Igo. G. Weston, C.Whitten. A. Wong. M. V. Hynes. J. McClelland. W.Bertozzi. J. M. Finn. C. E. Hyde-Wright. R. W. Lourie,P. E. Ulmer. B. E. Norum, and B. L. Berman. "Effective

T. Kobayashi. K. Nakai, R. Gilrnan, H. Baer. S. Greene.J. M. O'Donnel). H. T. Fortune, M. Kagarlis, K.Johnson, and S. Mukhopadyay, "Spectroscopy of theExotic Nucleus ' ' Li via Pion-DCX Reaction1 ' B(7T^,7t+)' ' Li." KEK Preprint 91-22 (submitted toPhysical Review Letters, 1991).

D. A. Krakauer. R. L. Talaga, R. C. Allen, H. H. Chen,R. Hausammann. W. A. Johnson, W. P. Lee, X-Q. Lu,H. J. Mahler, K. C. Wang, T. J. Bowles, R. L. Burman,R. D. Carlini, D. R. F. Cochran, P. J. Doe. J. S. Frank,M. E. Potter, E. Piasetzky, and V. D. Sandberg, "DirectExperimental Lower Bound on the Radioactive Lifetime ofthe Muon-Neulrino," Pins. Rev. D44 . R6 (1991).

D. A. Krakauer. R. L. Talaga, R. C. Allen, H. H. Chen,R. Hausammann, W. A. Johnson, W. P. Lee, X-Q. Lu,H. J. Mahler. K. C. Wang, T. J. Bowles, R. L. Burman,R. D. Carlini, D. R. F. Cochran, P. J. Doe, J. S. Frank,M. E. Potter. E. Piasetzky. and V. D. Sandberg. "Searchfor the Exotic Decay | i +

5 263, 534 (1991).-» Phvs. Lett.

D. A. Krakauer, R. L. Talaga, R. C. Allen. H. H. Chen,R. Hausamann, W. P. Lee, X-Q. Lu. H. J. Mahler. K. C.Wang. T. J. Bowles, R. L. Burman. R. D. Carlini, D. R.F. Cochran. P. J. Doe, J. S. Frank. M. E. Potter. V. D.Sandberg, and E. Piaselzky, "Limit on Flavor-ChangingNeutral Currents from a Measurement of Neutrino-Electron Elastic Scattering," Phys. Rev. D45. 975(1992).

D. A. Krakauer, R. L. Talaga, R. C. Allen. H. H. Chen.R. Hausammann. W. P. Lee. H. J. Mahler. X-Q. Lu. K.C. Wang. T. J. Bowles. R. L. Burman. R. D. Carlini. D.R. F. Cochran. P. J. Doe. J. S. Frank. E. Piaselzky, M.

E. Potter, and V. D. Sandberg. "Experimental Study of

1 13


Neutrino Absorption on Carbon," Phys. Rev. C 45, 2450(1992).

Daniel A. Krakauer, "Measurement of Neutrino ElectrinoScattering and Inverse Beta-Decay of Carbon UsingNeutrinos," Ph.D. thesis. University of California, Irvine,Los Alamos National Laboratory report LA-I2262-T(December 1991).

The L3 Collaboration, "Determination of ocs fromEnergy-Energy Correlations Measured on the Z°Resonance, Phys. Lett. 257B, 469 (1991).

The L3 Collaboration, "Search for the Neutral HiggsBoson," Phys. Lett. 257B, 450 (1991).

The L3 Collaboration, "Measurement of the InclusiveProduction of Neutral Pions and Charged Particles on theZ° Resonance," Phys. Lett. 259B, 199 (1991).

The L3 Collaboration, "Search for Leptoquarks in Z^Decays," Phys. Lett. 261B, 169 (1991).

The L3 Collaboration, "Measurement of Z0 —> bb Decaysand the Semileptonic Branching Ratio Br(b —» lepton +X)," Phys. Lett. 261B, J77 (1991).

The L3 Collaboration, "Measurement of ElectroweakParameters from Hadronic and Leptonic Decays of theZ°,"Z. Phys. C 51, 179 (1991).

The L3 Collaboration, "Search for Narrow High MassResonance in Radiative Decays of the Z*\" Phys. Lett.262B. 155 (1991).

The L3 Collaboration, "A Test of QCD Based on 3-JetEvents from Z° Decays," Phys. Lett. 263B, 551 (1991).

The L3 Collaboration, "Decay Properties of the TauLeptons Measured at the Z° Resonance, Phys. Lett.265B, 451 (1991).

The L3 Collaboration, "Measurement of the Lifetime of BHadrons and a Determination of IVct>l," Phys. Lett.270B. I l l (1991).

The L3 Collaboration, "Measurement of the StrongCoupling Constant ocs for Bottom Quarks at the Z°Resonance," Phys. Lett. 271B, 461 (1991).

J. Langenbrunner and C. Pillai, "Pion Produciion atSmall Angles," PILAC Technical Note No. 20, LosAlamos National Laboratory document LA-UR-91-1268(April 17, 1991).

D. M. Lee, W. W. Kinnison, and W. B. Wilson, "AMonte Carlo Calculation of the Neutron Flux in the LDetector" in Conference Record of the IEEE 1990 NuclearScience Symposium, Arlington, Virginia, October 22-27,1990), Vol. 2, p. 887.

M. J. Leitch, C. S. Mishra, H. W. Baer, A. Klein, Z.Weinfeld, E. Piasetzky, Y. Ezra, R. Weiss, J. R.Comfort, J. Tinsley, and D. H. Wright, "EnergyDependence of Low-Energy Pion Double ChargeExchange," Los Alamos National Laboratory documentLA-UR-91-3938 (submitted to Physics Letters, 1992).

M. J. Leitch, D. Aide, J. Boissevain, T. Carey, R.Jeppesen, J. Kapustinsky, D. Lane, J. Lillberg, P.McGaughey, J.-C. Peng, J. M. Moss, H. W. Baer, A.Klein, G. T. Garvey, C. Lee, M. Brooks, G. Brown, D.Isenhower, M. Sadler, R. Schnathorst, G. Danner, M.Wang, L. Lederman, M. Schub, C. N. Brown, W. E.Cooper, H. Glass, Y. B. Hsiung, C. S. Mishra, K.Grounder, M. R. Adams, G. Gidal, P.-M. Ho, M. Kowitt,K.-B. Luk, D. Pripstein, M. Apolinski, Guo, D. M.Kaplan, V. Martin, R. Preston, J. Sa, V. Tanikella, R.Childers, C. Darden, J. Wilson, R. L. McCarthy, Y.-C.Chen, G.-C. Kiang, P.-K. Teng, M. Bartlett, and G.Hoffmann, "Nuclear Effects on Heavy Quark Production,Results from Fermilab Experiments E772 and E789" (tobe published in the Proc. of Quark Matter 1991,Gatlinburg, Tennessee, November 11-15, 1991).

Z. Li, H. A. Thiessen, and H. A. Enge, "High-ResolutionBeam Lines for PILAC," PILAC Technical Note No. 9,Los Alamos National Laboratory document LA-UR-9I-231 (January 15, 1991).

Z. Li and H. A. Thiessen, "An Initial Design Study for aHigh-Resolution Spectrometer for PILAC," PILACTechnical Note No. 10, Los Alamos National Laboratorydocument LA-UR-91-301 (January 15, 1991).

R. A. Lindgren, B. L. Clausen, G. S. Bianpied, J.Hernandez, C. S. Mishra, W. K. Mize, C. S. Whisnant,B. G. Ritchie, C. L. Morris, S. J. Seestrom-Morris, C.Fred Moore, P. A. Seidl, B. H. WiJdenthal, R. Gilman,

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and J. A. Carr, "Pion Scattering to 6 Stretched Stales in2 4 Mg and 2 6 Mg" (submitted to Physical Review C,1991).

W. Louis, "Measuring the Quark Contribution to theProton Spin Through vp —» vp," in Proc. of Spin andIsospin in Nuclear Interactions, Telluride, Colorado,March 11-15, 1991, S. W. Wissink et al., Eds. (PlenumPress, New York, 1991), p. 341.

N. Mao and H. A. Thiessen, "Strong Quadrupole Magnetsfor the PILAC Injection Beam Line," PILAC TechnicalNote No. 24, Los Alamos National Laboratory documentLA-UR-91-1001 (March 18, 1991).

N. Mao and H. A. Thiessen, "Proposed Beam Line-AModifications for Proton Buncher for PILAC," PILACTechnical Note No. 19, Los Alamos National Laboratorydocument LA-UR-91-1120 (April 20, 1991).

N. Mao and H. A. Thiessen, "Proton Beam Transport forNeutrino Area and Isospin Laboratory Downstream of thePILAC Pion Production Target," PILAC Technical NoteNo. 33, Los Alamos National Laboratory document LA-UR-91-3185 (October 1, 1991).

N. Mao, and H. A. Thiessen, "PILAC General-PurposeBeam Line," PILAC Technical Note No. 34, Los AlamosNational Laboratory document LA-UR-91-3186 (October1, 1991).

Bjorn E. Matthias, "A New Search for Conversion ofMuonium to Antimuonium," Ph.D. thesis, YaleUniversity, Los Alamos National Laboratory report LA-I2202-TU991).

J. B. McClelland, "Summary of Low-Energy Aspects ofQCD and Medium-Energy Hadron Parallel Sessions," inProc. of the IV Conference on the Intersections betweenParticle and Nuclear Physics, Tucson, Arizona, May 23-29, 1991, Willem T. H. van Oers. Ed. (A1P Conf. Proc.243. American Institute of Physics, New York, 1992),p. 497.

J. B. McClelland, "A Pion Linear Accelerator at LAMPF:New Directions in Pion Physics," in Proc. of theInternational Workshop in Pious in Nuclei, Penyscola,Spain, June 3-8, 1991, E. Osel, M. J. Vicente Vacas, andC. Garcia Redo, Eds. (World Scientific, 1992), p. 83.

Publications

J. B. McClelland, T. A. Carey, L. J. Rybarcyk, W.Sailor, T. N. Taddeucci, X. Y. Chen, D. Mercer. S.DeLucia, B. Luther. D. G. Marchlenski, E. R.Sugarbaker, J. Rapaport, E. Gulmez, C. Whitten, Jr., C.D. Goodman, Y. Wang, and P. AI ford, "QuasifreePolarization-Transfer Measurements in the (p,n) Reactionat 500 MeV," in Proc. of the International Workshop inPions in Nuclei, Penyscola, Spain. June 3-8, 1991, E.Oset, M. J. Vicente Vacas, and C. Garcia Recio, Eds.(World Scientific, 1992). p. 93.

M. W. McNaughton. K. Koch. I. Supek. N. Tanaka, K.H. McNaughton, P. J Riley, D. A. Ambrose, J. D.Johnson, A. Smith, G. Glass, J. C. Hiebert, L. C.Northcliffe, A. J. Simon, D. L. Adams, R. D. Ransome,D. B. Clayton, H. M. Spinka, R. H. Jeppeson, and G. E.Tripard, "NP Elastic Spin Transfer Measurements at788 MeV," Phys. Rev. C 44, 2267 (1991).

M. W. McNaughton, "Nucleon-Nucleon Measurements atLAMPF," in Proc. of the lVth Conference on theIntersections between Particle and Nuclear Physics,Tucson, Arizona, May 23-29, 1991, Willem T. H. vanOers, Ed. (AIP Conf. Proc. 243, American Institute ofPhysics, New York, 1992), p. 1042.

D. J. Millener, M. B. Johnson, and J. A. McGill,"Hypernuclear Spectroscopy with the (7t,K) Reaction," inLAMPF Workshop on (K,K) Physics, AIP Conf. Proc.224, B. F. Gibbs, W. R. Gibbs, and M. B. Johnson,Eds. (AIP, 1991), p. 225.

A. H. Mohagheghi, H. C. Bryant, P. G. Harris, R. A.Reeder, H. Sharifian, C. Y. Tang, H. Tootoonchi, C. R.Quick, S. Cohen, W. W. Smith, and J. E. Stewart,"Interaction of Relativistic H~ Ions with Thin Foils,"Phys. Re". A 43, 1345 (1991).

C. Fred Moore, K. Johnson, G. P. Kahrimanis, JamesMcDonald, M. Snell, H. J. Ward, Sung Hoon Yoo. C. L.Morris, S. Mordechai, M. Burlein. N. Claylor, H. T.Fortune, R. Ivie, G. B. Liu, J. M. O'Donnell, D. Smith,N. Auerbach, and D. Robson, "Angular Distributions forthe Double Isobaric Analog and a T< Stale at HighExcitation in Pion Double Charge Exchange on 9 % b . "Phys. Rev. C 44, 2209 (1991).

S. Mordechai, C. L. Morris, J. M. O'Donnell, M. A.Kagarlis, D. Fink, H. T. Fortune, D. L. Watson. R.

1 IS


Gilman, H. Ward, A. Williams. Sung Hoon Yoo, and C.Fred Moore, "Analog of the T> Giant Dipole Resonancein Light Nuclei," Pins. Rev. C43, 1111 (1991).

S. Mordechni J. M. O'Donnell, M. A. Kagarlis, D.Smith, H. T. Fortune, C. L. Morris, H. Ward, K.Johnson, G. Kahrimanis, D. Saunders, and C. F. Moore,"Comparison of the Double Giant-Dipole States Observedin (Jt~,jt+) and (K+,K~) Reactions on 40Ca," Phys. Rev.C43 , R1509 (1991).

S. Mordechai and C. F. Moore, "Giant Resonance inSingle and Double Charge Exchange," in Proc. of theInternational Workshop in Pious in Nuclei. Penyscola,Spain, June 3-8, 1991, E. Oset, M. J. Vicente Vacas, andC. Garcia Recio, Eds. (Work! Scientific, 1992), p. 22.

C. L. Morris, "Nuclear Structure with Pions," Nucl Phys.

A 527, 433c (1991).

C. L. Morris, J. D. Zumbro, R. D. Ransome, B. G.Ritchie, D. L. Watson, and C. Fred Moore, "Evidence forPhysics Beyond the Quasi-Peuteron Model in PionAbsorption," in Proc. of the International Workshop inPions in Nuclei, Penyscola, Spain, June 3-8, 1991, E.Oset, M. J. Vicente Vacas, and C. Garcia Recio, Eds.(World Scientific, 1992), p. 495.

T. Muroga, H. L. Heinisch, W. F. Sommer, and P. D.Ferguson, "A Comparison of Microstructures in CopperIrradiated with Fission, Fusion, and Spallation Neutrons,"Los Alamos National Laboratory document LA-UR-91 -1269, presented at the Fifth international Conference onFusion Reactor Materials, Clearwater, Florida, November1991 (to be published in the Journal of Nuclear Materials,1992).

D. V. Neuffer, "A Lithium Lens for PILAC," PILACTechnical Note No. 6, Los Alamos National Laboratorydocument LA-UR-90-4132 (December 7, 1990).

L. C. Norlhcliffe, M. Jain, M. L. Evans, G. Glass, J. C.Hiebert, R. A. Kenefick, B. E. Bonner, J. E. Simmons,C. W. Bjork, and P. J. Riley, "Differential Cross Sectionfor n-p Elastic Scattering in the Angular Region 50° <0 * < 180° at 459 MeV," Los Alamos NationalLaboratory document LA-UR-91-2934 (.submitted toPhysical Review C, 1991).

J. M. O'Donnell and H. T. Fortune, "Isospin Splitting inDouble Isovector Excitations," Phys. Rev. C 44, 1481(1991).

J. M. O'Donnell, H. T. Fortune, and E. Rost, "0+ and 2+

Strengths in Pion Double Charge Exchange to DoubleGiant Dipole Resonances," Phys. Rev. C 44, 2426(1991).

R. D. Ransome, C. L. Morris, V. R. Cupps. R. W.Fergerson, J. A. McGill, A. Green, S. Dawson, D. L.Watson, J. D. Zumbro, B. G. Ritchie, J. R. Comfort, J.R. Tinsley, R. A. Loveman, P. C. Gugelot, and C. FredMoore, "Pion Absorption in Heavy Nuclei," Los AlamosNational Laboratory document LA-UR-91-1958(submitted to Physical Review, 1991).

R. D. Ransome, M. Martinez, V. R. Cupps, R. W.Fergerson, S. Dawson, A. Green, C. L. Morris, J. A.McGill, J. D. Zumbro, D. L. Watson, J. R. Comfort, B.G. Ritchie, J. R. Tinsley, R. A. Loveman, and C. FredMoore, "Inclusive Pion Single Charge Exchange onNuclei," Los Alamos National Laboratory documentLA-UR-91-3187 (to be published in Physical Review C,1992).

R. A. Ristinen, B. J. Kriss, S. H0ibraten, M. Holcornb,M. D. Kc ler, J. J. Kraushaar, S. P. Parry, A. Saunders,W. R. Srnythe, C. L. Morris, R. M. Whitton, J. T.Brack, J. L. Langenbrunner, and E. F. Gibson, "Pion-Proton Integral Cross Sections from 60 to 260 MeV" (tobe published in Proceedings of the Fourth InternationalSymposium on Pion-Nucleon Physics and the Structureof the Nucleon. Bad Honnef, Germany, September 9-13,1991).

R. Rusnak, E. R. Gray, R. G. Maggs, D. L. Schrage, A.Shaprio, G. Spalek and P. Wright, "SuperconductingCavity Development at Los Alamos NationalLaboratory," PILAC Technical Note No. 26, Los AlamosNational Laboratory document LA-UR-91-1466 (May1991).

M. E. Sadler, B. M. Brooks, L. L> Isenhovver. W. J.Briscoe, J. D. Bowman, D. H. Fitzgerald, and J. N.Knudson, "Forward- and Backward-Angle DifferentialCross Sections for Jt~p -> 7t°a at Tn = 10. 20, and40 MeV" (to be published in Proceedings of the Fourth

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International Symposium on Pion-Nucleon Physics andthe Structure of the Nucleon, Bad Honnef, Germany,September 9-13, 1991).

H. F.-W. Sadrozinski, N. Cartiglia, J. Dewitt, D. E.Dorfan, B. Hubbard, K. O'Shaughnessy, D. Pitzl, W. A.Rowe, A. Seiden, E. Spencer, P. Ferguson, C. M.Hoffman, W. W. Kinnison, E. C. Milner, W. F.Sommer, H. J. Ziock, P. Giubellino, and J. Ellison,"Radiation-Hard Front-End Electronics and SiliconMicrostrip Detectors" (submitted to the Symposium onDetector R&D for the SSC, Fort Worth, Texas, October15-19, 1990).

A. L. Sagle, B. E. Bonner, F. P. Brady, N. S. P. King,M. W. McNaughton, J. L. Romero, and J. L. Ullmann,"•'H + d <=> n + ^He Measurements and AbsoluteNeutron-Polarization Determination at 50 MeV," Nucl.Phys. A 530, 387 (1991).

D. P. Saunders, "Pion Elastic and Inelastic Scatteringfrom '^N," Ph.D. thesis, University of Texas at Austin,Los Alamos National Laboratory report LA-12183-T(1991).

M. E. Schillaci, "A Pulsed-Lepton Facility at LAMPF'sProton Storage Ring," in Proc. of a Workshop on Scienceat the Kaon Factory, David R. Gill, Ed., TRIUMF,Vancouver, British Columbia, Canada, Vol. 2, ParallelSessions, Sec 9 (July 23-28, 1990).

W. W. Smith, C. Y. Tang, C. R. Quick, H. C. Bryant,P. G. Harris, A. H. Mohagheghi, J. B. Donahue, R. A.Reeder, H. Sharifian. J. E. Stewart, H. Tootoonchi, S.Cohen, T. C. Altman, and D. C. Rislove, "Spectra fromMultiphoton Electron Detachment of H~," J. Op. Soc.Am. B 8, 17 (1991).

W. R. Smythe, "A Longitudinal Proton Beam Buncher forPILAC," PILAC Technical Note No. 12, Los AlamosNational Laboratory document LA-UR-91-294 (January16, 1991).

W. F. Sommer. P. D. Ferguson, and M. S. Wechsler,"Neutron Flux Enhancement at LASREF," Los AlamosNational Laboratory document LA-UR-91-3029, presentedat the Fifth International Conference on Fusion ReactorMaterials, Clearwater, Florida, November 1991 (to be

published in the Journal of Nuclear Materials. 1992).

Publications

W. F. Sommer, B. M. Oliver, and F. A. Garner. "HeliumProduction Rates in the LASREF Facility," SemiannualProgress Report. 1991, DOE/ER-0313/11.

G. Swain, "Choice of Operating Frequency for PILAC,"P1LAC Technical Note No. 17, Los Alamos NationalLaboratory document LA-UR-91-718 (February 19, 1991).

G. Swain. "Linac Reference Design for PILAC," PILACTechnical Note No. 14, Los Alamos National Laboratorydocument LA-UR-91-7! 7 (February 11, 1991).

G. Swain, "Cavity Shape and Beam Dynamics Design fora Linac for Pions," Los Alamos National Laboratorydocument LA-UR-91-1139 (submitted to 1991 IEEEParticle Accelerator Conference, San Francisco.California, May 6-9, 1991).

G. Swain, "PILAC: Superconducting Linac Design," LosAlamos National Laboratory document LA-UR-9J-J405(submitted to 1991 American Physical Society Meeting,Washington, DC, April 24-25, 1991).

John J. Szymanski. "The Production and Decay ofHypernuclei," Los Alamos National Laboratory documentLA-UR-90-3693 (submitted to the Proc. of the Conferenceon Particle Production Near Threshold, Nashville, Indiana.October 3, 1990).

T. N. Taddeucci, "Polarization Transfer in (p,n) Reactionsat 495 MeV," Los Alamos National Laboratory documentLA-UR-91-2402 (submitted to the 1991 InternationalConference on Spin and Isospin in Nuclear Interaction,Telluride, Colorado, March 11-15, 1991). and Nucl. Phys.A 527, 433c (1991).

C. Y. Tang, H. C. Bryant, P. G. Harris. A. H.Mohagheghi, R. A. Reeder, H. Sharifian, H. Tootoonchi,C. R. Quick, J. B. Donahue, Stanley Cohen, and W. W.Smith, "Threshold Structures in the MultiphotonDetachment Yield from the H~ Ion." Phys. Rev. Lett. 66,3124(1991).

C. Y. Tang, "Multi-Quanta Photodetachmenl from the H~lon," Ph.D. thesis, Univ. of New Mexico. Los AlamosNational Laboratory report LA-12254-T (1991).

H. A. Thiessen, G. Swain, G. Spalek. B. RuMiak, E.Gray. R. A. DcHavcn, J. K. Novak. H. Heinrichs. P.

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Grand, W. Harris, L. Young, H. Padamsee, H. Piel, andR. Sundelin, "Proceedings of the PILAC Cavity/RFReview," Los Alamos National Laboratory documentLA-UR-91-1668.

H. A. Thiessen, D. V. Neuffer, E. P. Colton, D. H.Fitzgerald, T. W. Hardek, R. L. Hutson, R. ). Macek. M.A. Plum, and T. Wang, "Observations of a FastTransverse Instability in the PSR," in Conference Recordof the 1991 IEEE Particle Accelerator Conference, SanFrancisco, California, May 6-9, 1991. 91CH3038-7(3),pp. 1896-1898.

H. A. Thiessen and T. W. Hardek, "Pinger System for theLos Alamos Proton Storage Ring," in Conference Recordof the 1991 IEEE Particle Accelerator Conference, SanFrancisco, California, May 6-9, 1991, 91CH3038-7(2),pp. 866-868.

H. A. Thiessen, D. V. Neuffer, E. P. Colton, D. H.Fitzgeraid, T. W. Hardek, R. L. Hutson, R. J. Macek, M.A. Plum, and T. Wang, "Observation of a Space ChargeEffects in the PSR," in Conference Record of the 1991IEEE Particle Accelerator Conference, San Francisco,California, May 6-9, 1991, 9ICH3038-7(3), pp. 1893-1895.

H. A. Thiessen and G. G. Karady, "A Novel Concept for aLithium Lens Exciter," in Conference Record of the 1991IEEE Particle Accelerator Conference, San Francisco,California, May 6-9, 1991, 9!CH3038-7(5), pp. 3132-3134.

H. A. Thiessen, "A Reference Design for PILAC: A PionLinac Facility for 1-GeV Pion Physics at LAMPF,"PILAC Technical Note No. 13, Los Alamos NationalLaboratory document LA-UR-91-869 (May 1991).

H. A. Thiessen, "PILAC: A Pion Linac Facility for I-GeV Pion Physics at LAMPF," in Conference Record ofthe 1991 IEEE Particle Accelerator Conference, SanFrancisco, California, May 6-9, 1991, 9ICH3038-7(5),pp. 3198-3200.

H. A. Thiessen, "PILAC: A Pion Linac Facility for1-GeV Pion Physics at LAMPF," in Proc. of the IVthConference on the Intersections Between Particle andNuclear Physics, Tucson, Arizona, May 23-29, 1991,Willem T. H. van Oers, Ed. (AIP Conf. Proc. 243,American Institute of Physics, New York, 1992), p. 446.

H. A. Thiessen, B. M. Han, and G. G. Karady, "TuningMagnet Current Conditions Systems for RF Cavity in aHigh Intensity Proton Accelerator," IEEE Transactions onNuclear Science 8, 1005 (1991).

H. A. Thiessen, "Optimum Injection Energy for PILAC,"PILAC Technical Note No. 27, Los Alamos NationalLaboratory document LA-UR-91-2022 (June 18, 1991).

H. A. Thiessen, A. Sreenivas, and G. G. Karady, "AGeneral Method of Resonance Power Supply Analysis,"IEEE Trans. Nucl. Sci. 39, 29 (1992).

H. A. Thiessen, "A Pion Linac Facility for I-GeV PionPhysics at LAMPF,'" Los Alamos National Laboratorydocument LA-UR-91-3134 (to be published inProceedings of the Fourth International Symposium onPion-Nucleon Physics and the Structure of the Nucleon,Bad Honnef, Germany, September 9-13, 1991).

H. A. Thiessen, B. Rusnak, J. McClelland, C. Morris, B.McCloud, J. O'Donnell, and J. Langenbrunner, "Test ofSuperconducting Radio-Frequency Cavity Bombarded byProtons," PILAC Technical Note No. 32, Los AlamosNational Laboratory document LA-UR-91-3513.

O. B. van Dyck, R. L. Hutson, M. E. Schillaci, and D.H. White, "Progress at LAMPF, January-December1990," Los Alamos National Laboratory reportLA-12256-PR (March 1992).

Y. Wang, C. D. Goodman, W. Huang, G. C. Kiang, R.C. Byrd, L. J. Rybarcyk, T. N. Taddeucci, J. Rapaport, D.Marchlenski, and E. R. Sugarbaker, "The (p,n)Measurements for Spectra Containing GT StrengthKnown from P Decay," Phys. Rev. C 35, 1666 (1990).

H. Ward, C. F. Moore, P. S. Maloney, and J. D. Martin,"Probabilistic Neural Nets in Analysis of MagneticSpectrometer Data," Los Alamos National Laboratorydocument LA-UR-91-2742 (accepted by NuclearInstruments and Methods, 1992).

H. Ward, K. Johnson, G. Kahrimanis, D. Saunders, C.Fred Moore, S. Mordechai, C. L. Morris, H. T. Fortune,M. A. Kagarlis, D. Smith, J. M. O'Donnell, and N.Auerbach, "The Double Giant Dipole Resonance in the(7t-,7t+) Reaction," Phys. Rev. C45, 2723 (1992).

118


D. H. White, "Neulrino-Hadron Physics and Summary ofNeutrino Program at BNL," in Proc. of a Workshop onScience at the Kaon Factory, TR1UMF, Vancouver,British Columbia, Canada, July 23-28, 1990, David R.Gill, Ed., Vol. 1 (1990).

D. H. White, "A Pulsed Lepton Source at LAMPF." inProc. of the IVth International Conference on theIntersections between Particle and Nuclear Physics,Tucson, Arizona, May 23-29, 1991, Willem T. H. vanOers, Ed. (AIP Conf. Proc. 243, American Institute ofPhysics, 1992), p. 452.

D. H. White, "Medium-Energy Neutrino Physics," LosAlamos National Laboratory document LA-UR-91-3830Ito be published in the Proc. of the Symposium on theFuture ofMuon Physics, Heidelberg, Germany, May 7-9,1991, Z. Phys. C, Particles and Fields (November 1991)).

D. H. White and H. A. Thiessen, "PILAC: A Pion LinacFacility for i-GeV Pion Physics at LAMPF," LosAlamos National Laboratory document LA-UR-91-3831[to be published in the Proc. of the Symposium on theFuture of Muon Physics, Heidelberg, Germany, May 7-9,1991, Z. Phys. C, Particles and Fields (November 1991)].

D. H. White, "A Pulsed Lepton Source at LAMPF," LosAlamos National Laboratory document LA-UR-91-3832[to be published in the Proc. of the Symposium on theFuture of Mnon Physics, Heidelberg, Germany, May 7-9,1991. Z. Phys. C, Particles and Fields (November 1991)|.

A. L. Williams, J. A. McGill, C. L. Morris, G. R.Burleson, J. A. Faucett, D. S. Oakley, M. Burlein, H. T.Fortune. J. M. O'Donnell, G. P. Kahrimanis, C. FredMoore, and S. Mordechai, "Pion Double Charge Exchangeon 4 2 - 4 4 - 4 8 Ca for 300 < T n < 550 MeV," Phys. Rev.C 4 3 , 766 (1991).

A. L. Williams, K. W. Johnson, G. P. Kahrimanis. H.Ward, C. F. Moore, J. A. McGill. C. L. Morris, G. R.Burleson. J. A. Faucett, M. Rawool-Sullivan, D. S.Oakley, M. Burlein. H. T. Fortune. E. Insko, R. Ivie, J.M. O'Donnell, and D. Smith. "Mass Dependence of High-Energy Pion Double Charge Exchange," Phys. Rev.C 4 4 . 2025 (1991).

A. L. Williams. "Pion Double Charge Exchange Abovethe A3/2.3/2 Resonance." Ph.D. thesis. University of

Texas at Austin, Los Alamos National Laboratory reportLA-12209-T(1991).

D. A. Williams, S. Barwick, R. L. Burman, M. Cavalli-Sforza, C. Y. Chang, D. G. Coyne. R. S. Delay, D. E.Dorian, R. W. Ellsworth, S. J. Freedman. B. F.Fujikawa, J. A. Goodman, T. J. Haines, C. M. Hoffman,D. A. Krakauer, P. W. Kwok, R. C. Lamb, X-Q. Lu. E.C. Milner, A. I. Mincer, D. E. Nagle, P. Nemethy. T. J.O'Neill, M. Potter, V. D. Sandberg, J. Sculli, C. Sinnis,R. Svoboda, O. T. Turner, D. H. White, D. D. Weeks, G.B. Yodh, W. P. Zhang, and A. Zych. "MILAGRO - ATeV Air-shower Array," in 22nd International CosmicRay Conference, Dublin, Ireland, August 11-23. 1991(Reprint, Ltd., Dublin, Ireland), Vol. 2, p. 684.

W. B. Wilson. T. R. England. W. W. Kinnison. andD. M. Lee, "Calculation of the Production and Decay ofRadionuclides in the Hadron Calorimeter of the L*Detector for the SSC," Los Alamos National Laboratorydocument LA-UR-91-999 (March 1991).

J. E. Wise, S. H0ibraten, R. J. Peterson, J. A. McGill,C. L. Morris. S. J. Seestrom-Morris, R. M. Whitton,J. D. Zumbro, and A. L. Williams. "Y-Scaling in 500-MeV Pion Quasielastic Scattering," Spring Meeting ofthe American Physical Society. Washington, DC, 1991,Bull. Am. Phys. Soc. 36, 1299 (1991).

Yi-Fen Yen, B. Brinkmoller, D. Dehnhard. S. M.Sterbenz, Yi-Ju Yu. Brian Berman. G. R. Burleson, K.Cranston, A. Klein, G. S. Kyle. R. Alarcon, T. Averctt,J. R. Comfort. J. J. Gorgen, B. G. Ritchie, J. R. Tinsley,M. Barlett, G. W. Hoffmann, K. Johnson, C. F. Moore.M. Purcell, H. Ward, A. Williams. J. A. Faucett. S. J.Greene, J. J. Jarmer, J. A. McGill. C. L. Morris, S.Penttila, N. Tanaka, H T. Fortune. E. Insko. R. Ivie. J.M. O'Donnell, D. Smith, M. A. Khandaker. and S.Chakravarti, "Asymmetry Measurement of Pion ElasticScattering from Polarized '-^C in the Energy Regioii ofthe [3,3| Resonance," Phys. Rev. Lett. 66. 1959 (1991).

V. W. Yuan, C. D. Bowman. J. D. Bowman. J. E. Bush,P. P. J. Delheij. C. M. Franfcle. C. R. Gould. D. G.Haase, J. N. Knudson. G. E. Mitchell. S. Penuila. H.Poslma, N. Robertson. S. J. Seestrom. J. J. Szymanski.and X. Zhu, "Parity Nonconservation in Polarized-NeulronTransmission through ' 39La," Phys. Rev. C 44. 2187(1991).

I ]9

Facility Development

ACCELERATOR COMPUTER CONTROL SYSTEM

A RADIOACTIVE BEAM FACILITY - A NEW INITIATIVE

DEVELOPMENT OF POLARIZED 7LI TARGET MATERIAL

LAMPF DATA ANALYSIS CENTER (DAC)

RF SYSTEM DEVELOPMENT

Facility DeuelopmentRccelerator Computer Control System

Accelerator computer control system

E. Bjorklund (Los Alamos)

The RIU MicroVAX system went into production forthe start of the 1991 run cycle. The RIU MicroVAXcontrols the RICE Interface Unit (RIU) which reads dataand issues commands to RICE modules along theaccelerator and experimental areas. RICE is the primary

data acquisition and control method for the LAMPFControl System (LCS). Prior to the RIU MicroVAX. theRIU was controlled by a PDP-11 computer that was tieddirectly to the main LCS control computer, as illustratedin Fig. I. This meant that any other control computers.

LCS CONTROLCOMPUTER

(ACCR)

PSR CONTROLCOMPUTER(PSRMV2)

ICR CONTROLCOMPUTERS

(IA. IB, IC)

ETHERNET

PDP-11

RIU

RICE RICE

DLJ

RICE

L

RICE

ilLJ

L

RICE

n LJ

RICE

Fig. I. Previous configuration with PDP-I I. All RICE data go through main LCS control computer.

122

Facility Deuelopmentaccelerator Computer Control System

LCS CONTROLCOMPUTER

(ACCR)

PSR CONTROLCOMPUTER(PSRMV2)

ICR CONTROLCOMPUTERS

(IA. IB. IC)

ETHERNET

RICE

us- - - . . . PL

D

RICE

y f j ,j D

RICE

"OS

"° " ..

RICE RICE RICE

Fig. 2. New configuration with RIU MicroVAX. RICE data are directly available to all control computers.

such as the ones servicing the consoles in the InjectorControl Room (ICR), were required to go through main.LCS control computer to obtain any RICE data theyneeded. This placed an undesirable load on main LCScontrol computer and also created a bottleneck for accesslo RICE data.

The RIU MicroVAX makes RICE data directlyavailable to any control computer on the Ethernet asshown in Fig. 2. The increased memory and processing

power also make it possible to do certain globaloptimizations that were not possible on the old system.Techniques such as background polling of frequentlyrequested channels, queueing so that several requests canbe satisfied from a single read, and allowing requests to begrouped into "aggregates" have significantly improved theperformance of the control system monitoring andarchiving programs.

Facility DeuelopmentRadioactiue Beam Facility

A radioactive beam facility - a new initiative

W. L. Talbert, D. J. Vieira, and J. M. Wouters (Los Alamos)

The potential research opportunities using intenseradioactive beams, briefly stated in the previous Progressat LAMPF 1990, continue to generate much excitementthroughout the world-wide nuclear science community.During 1991, several conferences and workshops were heldwith sessions devoted to scientific and technical aspects ofradioactive beam research. Additionally, the NorthAmerican Steering Committee, formed following the LosAlamos workshop in April, 1990, released a report,"IsoSpin Laboratory (ISL) - Research Opportunities withRadioactive Nuclear Beams," in which physics researchtopics are presented along with a suggested bench markfacility and areas where R&D is needed.'

Al LAMPF, a proposal to address some of the R&Dissues associated with the production of radioactive beamshas been approved (Exp. 1257), and in the September1991 LAMPF Newsletter the formation of a RadioactiveBeams Working Group was announced. An activeprogram at LAMPF to support the ISL initiative has thusbeen initiated. The purpose of this article is to provide asynopsis of the world-wide activities in radioactive beams,to outline the LAMPF activities (including a briefdiscussion of the goals of Exp. 1257), and to invite thoseinterested in participating in these activities to join thenew working group.

An important milestone for the radioactive beamscommunity was reached last year with the publication ofthe report on the IsoSpin Laboratory initiative by theNorth American IsoSpin Laboratory Steering Committee.This document' has been widely distributed throughoutthe community (additional copies are available, uponrequest) and offers a broad view of the exciting research

opportunities in nuclear physics, nuclear astrophysics, andmaterials sciences made possible by an ISL.

The science of the ISL can be subdivided into twobroad categories, low-energy nuclear physics, anddisciplines using nuclear physics techniques and/or results(i.e., astrophysics, atomic physics, and materials science).A key area of research in low-energy nuclear physics is thestudy of exotic nuclei with extreme N/Z ratios. Thesenuclei have unexpected shapes such as the prolatelydeformed 3 ' Na or unusual matter distributions such thosefor Li, Be, and B, which exhibit neutron halos.Reaction studies using radioactive beams will contributein important new ways to our understanding of the nuclearstructure of these and other important nuclei not nowaccessible. Creation of a whole range of nuclei at highspin will lead to a better understanding of collectivity andprovide access to specific orbitals leading to very unusualshapes such as in hyperdeformed nuclei. Regionscontaining the N = Z nuclei up to Sn or thesuperheavy element nuclei will finally become accessible.Unusual heavy-ion reactions using, for example, neutron-halo nuclei will be possible, which will lead to neutronflow phenomena, neck formation in fusion reactions, andthe availability of high Q-value reactions. For proton-richnuclei, charge-exchange reactions in heavy-mirror nucleiwill become possible. Another area of interest is inprecision tests of the electroweak Standard Model viaparity nonconservation measurements in atomic and |5-decay transitions.

Nuclear astrophysics has always had a symbioticrelation with low-energy nuclear physics. At ISL therewill be an opportunity for an explosion of new studiesbeginning with measurements of reaction rates for the

124


1 = Atomic Physics2 = Materials Science and

Solid State Physics3 = Nuclear Astrophysics4 = Nuclear Physics

3 + 4 <*

E=10MeV/ul<1011 part./s for Z < UHigh Beam Purity

DTL2

Stripper-

1 +4

1 +4

d Stripper

RFQ1 RFQ2 DTL1

H.V. = +180kV-54

E = 60 keVE=100keV/u

E=10keV/u

E=1.5 MeV/u

TargetIon Source

m- '0.5 - 1 GeV 0.1mA Proton Accelerator

Fig. 1. Schematic layout of a possible approach to a radioactive beams facility, indicating the types of physics studiespossible at each stage.

fusion reactions occurring in older-age stars. New results(e.g., masses, half-lives, and reaction rates) at the limitsof stability will greatly enhance our understanding of therp-, s-. p-, and r-processes. In particular, such measure-ments will help determine the sites, environments, andtime scales for nucleosynthesis in supernova.

Atomic physics and materials science will benefitfrom the availability of a wide range of new probes thatcan be chosen for half-lives, decay energies, andbombarding energies. Used as dopants in materialsscience, high-specific-activity beams will permit time-dependence of reactions to be studied at low-dopant levels,thus reducing interfering collateral damage. All of thesestudies will, in the words of the ISL report, "revealwholly new horizons for this [nuclear science] and relatedtopics."

The report also contains a discussion on theproduction of radioactive beams, and presents, as apossible concept, a two-accelerator approach, with the

accelerators coupled together by an on-line mass separator(ISOL) employing a thick (~1 mole/cm") productiontarget. This approach, chosen as achievable usingessentially proven technology, requires a primary proton(and possibly • He) accelerator providing beams withenergies of up to 1000 MeV and currents of up to100 |iA, and a post-accelerator similar to existing heavy-ion accelerators (perhaps the best example is the ATLASfacility at Argonne National Laboratory). The ISOLsystem and associated production target is based largely onexperience at the CERN ISOLDE facility. A schematicillustration of the radioactive beam facility is seen inFig. 1, in which not only the components of the facilityare indicated, but also indicating the types of physicsstudies that could be pursued at various stages of thefacility.

Two international conferences in 1991, the SecondInternational Conference en Radioactive Ion Beams, heldin Louvain-le-Nueve. Belgium, and the Twelfth

125


International Conference on Electromagnetic IsotopeSeparators, held in Sendai, Japan, featured presentationson the ISL initiative, and were well attended.

A workshop on radioactive ion beams was held inEast Lansing in October, in conjunction with theDivision of Nuclear Physics Meeting, and featured asession on the ISL report. This workshop was the mostheavily attended workshop ever to be sponsored by theDivision of Nuclear Physics at its annual fall meeting.These conference activities illustrate the growing interestin radioactive beams by the nuclear physics community.The ISL users community, started in 1990, currentlynumbers over 400 members worldwide.

A special symposium on Production and Utilizationof Radioactive Nuclear Beams was held at the AmericanChemical Society National Meeting in San Francisco inApril, 1992. An ISL technical workshop is alsoscheduled for October 1992 at Oak Ridge.

At LAMPF, our activities have taken severaldirections. First of all, a Radioactive Beams WorkingGroup has been formed with strong initial response andenrollment now exceeding 50 members. This workinggroup was established to provide an organizationresponsive to the work on radioactive beams at LAMPF.The acting chairman for this working group is P. E.Haustein of Brookhaven National Laboratory, and W. L.Talbert. D. J. Vieira, and J. M Wouters are local (LANL)contacts. Secondly, we are in the process of formingstudy groups to examine possible approaches to ISLimplementation at LAMPF. These will develop thetechnical pre-concept and prototypical approach, andselected scientific experiments. Progress in both areaswill be reported at the ISL technical workshop in OakRidge.

As mentioned above, Exp. 1257 was approved duringthe August 1991 PAC r.ieeting. and is the first ISL-relatedexperiment at LAMPF. The technical goals of theexperiment are to:1. provide a test of a thin-target, He-jet activity transport

(mounted in the primary 1-mA proton beam in theA6 beam slop area) that could provide acomplementary production approach to that in theISL report (which employs a thick target patternedafter the ISOLDE experience).

2. measure the yields of exotic nuclei from a thinuranium or thorium target, and

3. determine the operational and reliability characteristicsof this approach.

The physics goals of the experiment are to:1. use the He-jet activity transport line for studying

neutron-rich isotopes of refractory elements aroundmolybdenum, by use of fast radiochemical separation(using an apparatus called SISAK-), andsystematically map the nuclear shape transition above90Zr, and

2. obtain samples of the same refractory element regionfor off-line low-temperature nuclear orientationmeasurements of nuclear moments.

An additional goal of these studies is to develop a coreusers group who would actively participate in this He-jetR&D program.

For the next one to two years, activities fori£xp. 1257 will concentrate on the design and constructionof the He-jet target chamber, the activity transport line,associated detector station, and helium recovery system.We will also need to define the details of the physicsmeasurements, to prepare for the measurements, and totest the full system prior to, and with LAMPF operation.

It is clear that research using radioactive beams is atimely and exciting idea. At LAMPF, we are embarkingon a program in support of the research and developmenttopics identified in the ISL report with Exp. 1257 andpossible follow-on activities, and with the formation ofstudy groups to identify a pre-conceptual design for aradioactive-beams facility based at LAMPF, and to furtherdevelop and refine the physics case. We are very muchinterested in involving LAMPF users in this endeavor,and in having an active interaction with potential usersfrom all interested communities (nuclear science,astrophysics, atomic physics, and material sciences). Aninvitation is extended to all interested individuals to joinour effort.

References

1. North American Steering Committee et al., "TheIsoSpin Laboratory (ISL) - Research Opportunitieswith Radioactive Beams," Los Alamos NationalLaboratory report LALP 91-51 (October 1991).

2. H. Persson, G. Skarnemark. M. Skalberg. J. Alstad.J. O. Liljcnzin, G. Bauer. F. Haberberger, N.Kaffrell, J. Rogowski, and N. Trautmann."SISAK 3 - An Improved System for Rapid Radio-chemical Separations by Solvent Extraction,"Radiochim. Ada 48, 177 (1989)

126

Facility DeuelopmentPolarized Target Material

Development of polarized 7Li target material

J. Estes, K. Graham, J. J. Jarmer, T. Langston, S. Penttila, and D. Yeamans (Los Alamos)

A variable temperature cryostat has been constructedto cool polarized target materials during beam irradiation.With the cryostat samples of 7LiH were irradiated withelectrons. Polarization tests showed lithium polarizationslarge enough to be usable in nuclear scatteringexperiments.

Nuclear polarization can be highly enhanced by meansof microwave dynamic nuclear polarization (DNP).1

Paramagnetic centers, necessary for the microwave DNPprocess, may be introduced in target material, either bychemical doping or ionizing irradiation. Chemical dopingrequires a target-material that is a good solvent for aparamagnetic dopant such as EHBA-Cr(V).^ The materialshould be an easy glass-former to facilitate uniformdistribution of the dopant when the material is solidifiedby freezing. Chemical doping is well understood and hasbeen successfully used for both proton and nucleartargets.3 At present, irradiation has been used to preparegood polarized proton and deuteron targets from NH3 andND3.4"6 A group at Saclay has shown that high 6Li and7Li polarizations can also be obtained by irradiating 6LiDand 7LiH with electrons.7 During irradiation of solidmaterial, paramagnetic centers are created throughionization mechanisms. The material must be maintainedat reduced temperature to prevent the centers fromdiffusing and recombining. It has been observed that foroptimum polarization, the irradiation temperature iscritical and varies with different materials. Liquid argontemperature (90 K) is best for NH3 (Ref. 4) and about180-190 K works for 7LiH. 7 For good polarization, adose of over I01 7 charged particles per cm2 of material istypically needed.

LAMPF Exps. 1172 and 1206 requested polarizedlithium targets. Therefore, apparatus was built to prepare

FlowGauge

I rJn I

- Turbine

- Vacuum

HeliumGas

- LiquidNitrogen

- Thermo-couples

Target

Heater

Fig. I. Cryostat for preparation of irradiated targetmaterials.

irradiated target materials at different temperatures. Withthis apparatus, shown schematically in Fig. 1, targetmaterials can be irradiated from liquid argon temperature

127

Facility DeuelopmentPolarized Target Material

CM

o

O

X

CO

o•§

111

1 .6

1.4

1.2

1.0

0.8

0.6

0.4

0.2

0.0

I I

—

—

—r^rS-10 -8 -6

i i i i

/ \

/ \

/ \

1 \? \1 h/ ' • ̂

/

v 1

! Targeti

- 4 - 2 0 2

Radius (cm)

1 1 1 1

• TLDs behind Cryostata = 4.1cm —

• TLDs in front of Cryostato = 2.1cm

-

\

\ ^ i l —4 6 8 10 12

Fig. 2. Beam profiles for a single pulse measured by TLD arrays separated by 21 cm. Arrays were located immediately infront and behind the irradiation cryostat. Integrated areas represent 2.1 x 10^ electrons. Transmission of'30-MeV electrons isabout 0.9 with material thickness of 1.91 gcvw .

up to room temperature. Above argon temperatures thematerial is cooled by circulating helium gas with a turbineinside the cryostat or in a closed loop with a compressor.The helium-gas temperature is measured below and abovethe sample with thermocouples. A thermocouple can alsobe mounted inside the sample. Before and after anirradiation the temperature sensors were calibrated withliquid nitrogen.

To improve cooling during both the irradiation andthe DNP polarization process, the 7LiH material wasmade in the form of small chunks of nominal size about1 mm. Three separate irradiations were performed at theWhite Sands Nuclear Effects Facility using a 30-MeVlinear electron accelerator. The beam was pulsed with apulse length of 10 |_ts and repetition rate of 30 Hz. Thebeam emerging from the linac was very divergent. This

was used to adjust the size of the beam spot on a sampleby locating the cryostat at the appropriate downstreamposition (see Fig. 2). A typical average current on asample was about 0.2 iiAcirr^. About 24 h were neededto achieve a dose of 10 ' 7 electrons per cm-. The currentwas limited because of the finite cooling to the sample.The beam current was measured by a beam monitorlocated before the exit window of the linac. The monitorwas calibrated with a Faraday cup and thermoluminescentdosimeter (TLD). Figure 2 shows beam profiles measuredwith TLDs for a single beam pulse. The TLD arrays weremounted immediately in front and behind the cryostat andwere separated by 21 cm.

Table I presents irradiation conditions for differentsamples and results of polarization tests performed in adilution refrigerator a! 2.5-T field. The magnetic field

128

Sample#

Table I.

Irradiated Temperature(K)

Irradiation Conditions

Dose(ID17 ecnT2)

and 7Li Polarization

Irradiation Rate(1013 ecnr2s-')

FacilityPolarized

Results.

Polarization (+)

DeuelopmentTarget Material

Polarization (—)

1234

203 ± 4194 ±4184 ±4180 ±2

3.62.50.52.1

1.31.10.40.2

23 ± 221 ± 231 ±2

-

-18 ± 2-

-31 ±2-29 ±2

deviation over the target samples was less than 12 gauss.The microwave frequencies used to polarize were 70.014GHz for positive polarization and 70.136 GHz fornegative polarization. During polarization the coolanttemperature was 0.2-0.4 K. Polarization buildup timeswere very long; to obtain maximum polarization forsample #3, 24 h were used.

The polarization values obtained are already usable innuclear scattering experiments; however, more tests withthe material are needed to better understand the polarizationbehavior. With the present dose levels, it may bepossible to shorten the polarization buildup time by usingdifferent DNP conditions such as higher field (5 T) andwarmer temperatures (1 K). as has been observed withNH3.? The maximum lithium vector polarization of 0.31corresponds to a proton polarization of only 0.46, whichis low and can be expected to go higher.

References

1. A. Abragam and M. Goldman, Nuclear Magnetism:Order and Disorder (Clarendon Press, Oxford, 1982).

2. M. Krumpolc and J. Rocek, J. Am. Client. Soc.101, 3206 (1979).

3. S. Penttila, J. J. Jarmer, N. Tanaka, M. B. Barlett.K. Johnson, G. W. Hoffmann et al., in The 9thInternational Symposium on High Energy SpinPhysics, Bonn'90, W. Meyer, E. Steffens, and W.Thiel, Eds. (Springer-Verlag Berlin Heidelberg,1991), Vol. 2: Workshops, p. 315.

4. The Proceedings of the 4th International Workshopon Polarized Target Materials and Techniques, W.Meyer, Ed. (Physikalisches Institut Universilat Bonn.1984).

5. D. G. Grabb, C. B. Higley, A. D. Krisch, R. S.P:\ymond, T. Roser, and J. A. Stewart, Phys. Rev.Lett. 64, 2627 (1990).

6. E. Giilmez, D. L. Adams, S. Beedoe, M. Bleszynski,J. Bystricky, V. Ghazikhanian et al., Phys. Rev. C45, 22 (1991).

7. P. Chaumette, J. Deregel, G. Durand. J. Fabre. L.van Rossum, in The 8th International Symposium onHigh-Energy Spin Physics, 'SH. Kenneth J. Heller.Ed. (AIP Conf. Proc. 187, 1989). p. 1275.

Facility DeuelopmentLHMPF Data Hnalysis Center (DHC)

LAMPF Data Analysis Center (DAC)

M. E. Potter, A. G. Chavez, J. A. Faucett, J. F. Harrison, E. E. Martinez, and S. C. Trujillo (Los Alamos)

During 1991, the DAC continued to respond to userneeds by increasing the available processing power,improving network access and connectivity, and providingnew Unix capability.

In order to increase the computing capacity availableto users, two new Digital Equipment Corporation (DEC)VAXsiation 3100 Model 76s were added to the DACVAXcluster. Each of these workstations has a processingpower equal to the VAX 8650 mainframe (MPXO).Although interactive logins are not allowed on these newworkstations, a special batch queue calledSYSSCOMPUTE was set up to allow users to executeCPU-intensive batch jobs on the workstations. Theseworkstations are also responsible for performing the daily,weekly, and monthly backups onto 8-mm tape during thenight. These backups were previously performed on aMicroVAX-ll class computer (MPBACK). Moving thebackups to the new workstations has more than halved thetime needed for backups.

The DAC VAXes remained at virtual memory system(VMS) version 5.4 during the year. In order to improvecompatibility with the DAC cluster, all other VMScomputers in MP Division were upgraded to VMS 5.4before the run cycle was begun. In addition to VMS 5.4.the Multinet networking software was installed on allVMS computers to allow communication over theinternational Internet using TCP/IP. In order to performthe close to sixty system upgrades in a timely manner, theDAC developed an upgrade procedure using the network,allowing VMS to be installed in only one-half hour percomputer, compared to the several hours that it wouldnormally haven taken. In addition, by "cloning" astandard system configuration onto each computer, and

providing a well-defined way to customize each system,the system management load at the DAC was reduced.

In addition to upgrading the VMS operating systemin the counting houses and installing Multinet networkingsoftware, a few counting houses were outfitted with an 8-inm tape system, replacing the large 9-truck tape drives inthese counting houses. Each of these counting houseswas also equipped with a one-gigabyte disk drive forstaging data before it is written to tape. These systemswere successfully used in several MP-10 experimentsduring the last year. Each 8-nim cartridge will hold asmuch data as 14 6250-bpi tapes. In addition, the low costof the tape drives has made it possible for universities toacquire drives in order to read these data tapes. There areplans to outfit more counting houses with this technologyin 1992.

Network connectivity and performance at LAMPFwere significantly improved in 1991:

• The central DAC VAXclusler was connecteddirectly to the national High-Energy and NuclearPhysics Network (HEPnet). rather than beingconnected indirectly through machine ESSDPI.This allows other sites in the nation to directlylog in or access files at the DAC and allows directaccess by remote X-window users.

• The 64-Kbits/sec network link to the Computingand Communications Division (C Division) wasimproved to a speed of 256 Kbits/sec. The DACpurchased a Cisco Router to handle the DECnetand Internet routing between I.AMPI- and CDivision, improving the reliability of the networkconnection to C Division, and preparing I.AMPhfor future network enhancements.

130

Facility Deuelopment

• Improving the connectivity of the DAC to thedesktop was another goal in 1991. To improvecommunication with Macintosh users, several ofthe private Loealtalk networks were connected tothe DAC Ethernet backbone. DEC Paihworks forMacintosh software was purchased to supplementthe existing AlisaTalk software. This softwareallows Macintosh users to access the disks at theDAC as if there were local disks connected to theMac. In addition, this software allows Macintoshusers to print to almost any printer located on-site.

• To improve communication with IBM-compatiblePersonal Computers (PCs), the DAC begansupporting the PC/TCP software from FTP, Inc.,allowing a PC to connect tc the national Internetand communicate to VMS computers on-siterunning the Mullinet software.

• The DAC worked closely with the ComputerMaintenance group (COMA1NT) in 1991 toimprove the reliability and performance of theLAMPF network. A Hewlett-Packard EthernetMonitoring system was purchased to help detectand isolate network problems. The monitoringpackage has paid for itself many times already byenabling the computer staff to detect and correctseveral network problems before they were noticedby users or brought the network down.

Based upon the results of a user survey, the printingcapacity at the DAC was enhanced in 1991 through thepurchase of three high-speed Talaris Laser printers.Although additional hardware is being purchased toenhance the PostScript speed of these printers, they havebeen functioning well as high-speed substitutes for theDEC LN03 laser printers on-site.

LflMPF Data Rnalysis Center (DRC)

Also due to user requests. Unix support was added tothe DAC in 1991. Two Digital DECstalion 5OOO/2OOworkstations running Ultrix, DEC's variation of Unix,were added to the DAC network. These workstations havefull access to the disks on the DAC VAXcluster throughthe use of the Network Eile System (NFS) and theMultinet software on the VMS machines. Each of theseworkstations has a processing power three times that ofthe LVAX 8650 mainframe, and can handle 32 interactiveusers. Additional software, such as the CERN programlibrary, and the TeX/LaTeX document preparation system,was installed on these machines to make them moreuseful to users. Currently, the use of these workstationshas been low. but is expected to increase in 1992. Theprimary Ullrix workstation, DACDSO. is also configuredas a boot server, allowing other Ultrix machines atLAMPF to boot without having a local copy of theoperating system. This client/server architecture hasallowed the DAC to support many more workstationsthan would otherwise have been possible given the limitedstaffing levels in 1991.

In the LOB and DAC terminal rooms, the agingterminals were replaced by new GraphOn terminals. Thischange, in turn, provided more spare VTlOOs forComputer Maintenance in order to maintain the oldterminals still found in some counting houses.

Finally, in order to improve communication betweenthe DAC staff and the DAC users, the DAC newsletter,"Computing at LAMPF." was resurrected. Thisnewsletter is published several times each year and helpskeep users posted on happenings at the DAC. When thefirst issue was published, in September of 1991. a newDAC user handbook was also written, and both weremailed to all DAC users.

Facility DeuelopmentRF System Deuelopment

RF system development

R. Cliff (Los Alamos)

The four rf generators for the 201-MHz section ofLAMPF are four-stage vacuum-tube amplifiers. Adiagram of a single generator module is shown in Fig. I.

Each amplifier chain is driven by a small interfaceamplifier (IFA) and consists of a three-stage intermediatepower amplifier (IPA) and a final power amplifier (PA).

PlateSupply

PlateModulator

H VSupply

1 1ScreenSupply

PlateSupply

ScreenSupply

II 1 IIGrid

SupplyScreenSupply

ScreenModulator

III II IIPowerSupply

GridModulator

GridSupply

GridSupply

PlateModulator

I I I I I I I I IPulse

Modulator

I C A

FilamentSupply

765-T^>

FilamentSupply

765?^>

IDA

Filamentoupply

4616*^>

I

FilamentSupply

783E

p/

>

Fig. 1. Diagram of the 201-MHz amplifier chain.

132

Facility Deuelopment

75 76 77 78 79 80 81 62 83

Year

Fig. 2. Ratio of 201-MHz downtime to thai for H05-MHzmodules.

RF System Deuelopment

0 10 20 30 40 50 60 _

Time After Tube Filaments Turned On (min) <

Fig. J. 7835 vacuum improvement with Penning gaugepumping.

Each of the tube-amplifier stages is run by several dcpower supplies. There are also several pulse modulatorsin each module. Failure of any tube, supply, ormodulator in any of the four amplifier modules causes anaccelerator shutdown.

The 201-MHz systems have been responsible for anaverage of one-third of the accelerator downtime over thepast .seven years. As depicted in Fig. 2, (he four 20)modules cause double to triple the downtime caused by theforty-four 805-MHz rf modules. The PAs have caused thegreatest loss of running lime and the IPAs have caused thesecond greatest loss.

A program to increase the reliability of the PAs is inprogress. A system for on-line replacement of an entirePA is in development; purchase of highly regulated PA-filament power supplies is planned; and development of asolid-state replacement for the PA-modulator driver isbeing studied. The first project is expected to be completein time for the FY93 production period. Scheduling ofthe last two items is contingent upon funding.

Failures of the 7835 vacuum tube in the PA continueto be a very serious problem. Three problem areas arenow recognized with some confidence. First, it appearsthat we have in the past operated some tubes withinsufficient rf conditioning; second, there were somemanufacturing problems during a period approximatelyfrom 1988 through 1989; and third, the high 201-MHz rfduty factor has caused ceramic insulator failures in thetube.

It is felt that problems in the first area have beensolved. We have begun to purchase tubes incorporatingPenning ion gauges (called "vacion pumps" in generalusage). We have accumulated several thousand hours ofexperience with these new tubes. We now use the tubevacion gauges to determine that rf conditioning iscomplete before beginning full-power operation. We alsouse the gauges to "pump" the tubes down more quicklyfor more rapid return to operation, as illustrated in Fig. 3.After further study, additional procedure changes may bedeveloped in other areas of tube operation.

It appears that the second problem has been solved forus. A deterioration of tube vacuum quality was noticed atBrookhaven beginning about 1988. Immediate steps weretaken to correct some manufacturing processes and toimprove tube materials and parts quality. In 1990, newand rebuilt lubes tested at Brookhaven were performing inan excellent manner.

A solution to the third problem has not yet beenfound. Cracking of 7835 ceramic insulators is nowrecognized as the dominant type of failure lor this tube atLAMPF. The material and quality difficulties mentionedabove probably aggravated this problem in tubesmanufactured during the 1989 to 1990 period. However,the onset of the problem correlates well with our dutyincrease beginning about 1982, although our picture isinconclusive. This is illustrated by year of manufacture inFig. 4 and by year of failure in Fig. 5.

Facility DeuelopmentRF System Deuelopment

Fig. 4. Manufacturing years of 7835 tubes that

experienced plate insulator failures.

Fig. 5. Failure years of 7835 tubes that experienced plate

insulator failures.

rj lie 7835 tube was originally developed for service inlow-duty radar applications. No other users of this tubehas ever approached the LAMPF duty requirement and noother user has experienced ceramic failures. Modificationsto the tube are being considered in an effort to increase itsability to withstand the higher duty required at LAMPF.

Failures of 7651 tetrodes in the IPA have increasedsubstantially during (he last several years. The associatedpower supplies have also caused problems for a number ofyears. A solid-state amplifier to replace both 7651 stagesis in development. Installation of these amplifiers in allfour modules is planned to be complete before the FY93

run. A solid-state plate supply for the 4616 tetrode,which will permit elimination of its plate modulator, isplanned. Initiation of this project will depend onavailability of funding.

A number of smaller, additional modifications to the201-MHz systems are anticipated. Improvement of high-voltage cabling and connectors is in progress. Automateddiagnostic and performance monitoring of the systemswith a dedicated MicroVAX computer is planned. Theobjective of the upgrade program is to increase 201-MHzsystem beam-support availability to 98% or more.

134

Environment, Safety, and Health

ES&H

Environment, Safety, and Health

J. E. Little and E. Bush (Los Alamos)

Tiger Visit

The Doe Tiger Appraisal at LANL was conductedduring October and November of 1991. Auditors from theaccelerator team, the management team, and theenvironmental team interviewed employees and inspectedthe LAMPF facility. The appraisal was generallybeneficial. The auditors were knowledgeable andprofessional and were willing to share their expertise.LAMPF received a few category 2 violations and manycategory 3 and 4 violations.

• Category 1 violations were issued for situationswhere there was an immediate danger to life andhealth.

• Category 2 violations were issued for code violationssuch as exposed electrical power terminations.

• Category 3 & 4 violations were issued where rulesand regulations or "best practices" were not followed.

As a result of the Tiger visit, efforts were initiated toimprove the environmental monitoring of the LAMPFstacks, to correct all Category 2 OSHA violations, toimprove emergency egress from Technical Area 53(TA-53). and to control TA-53 access via a manned gate.

In response to a "Tiger" finding, dealing with lifesafety issues in the LAMPF beam tunnels, an accesscontrol system was implemented. This involved lockingthe tunnels and granting access only to persons who havereceived tunnel-specific training and obtained authorizationfrom the owner Group Leader. The training involvedidentification and mitigation of the hazards, specifyingescape routes and phone locations, and identifying other

special-entry requirements such as personal protectiveequipment.

Radiation Safety Committee

The radiation safety committee issued a LAMPFPROMPT RADIATION PROTECTION policy andshielding guidelines in addition to reviewing the LAMPFbeam lines for adequate shielding and for compliance withthe personnel safety systems guides.

TA-53 ES&H Team

A TA-53 ES&H Team has been established with thesupport of the ADPLS. This team has site-wideresponsibility and authority to assist the lineorganizations to solve theii £S&H problems as well as toascertain and interpret LANL and DOE rules, regulations,and policies. Team members have expertise in OSHA,industrial safety, laser safety, cryogenic safety, industrialhygiene, training, environmental issues, radiationprotection, and chemical safety.

Training Activities

An MP-Division training office has been established.It has developed and is administering a TA-53 Facility-Specific Training for MP Users. The 2-1/2-hour classcovers the major hazards at TA-53 and (heir mitigation.Other courses available to users include:

138

ES&H

Radiation Worker TrainingCertification ProgramsSite Specific TrainingHazardous Chemical CommunicationLock and Tag for MP Division

The Laboratory, in response to the new OSHArequirements for control of hazardous energy, developed apolicy defining in broad terms methods to control thesesources. A more definitive implementation plan has beendeveloped for 1VIP Division use.

Modifications to the Radioactive AirExhaust System

A Conceptual Design has been completed for asystem that will reduce the emission of radioactive air tothe atmosphere at LAMPF by a factor of approximatelyfive. The system will accomplish this reduction by"delaying" the discharge of several short-livedradioisotopes to the LAMPF exhaust stack. The existingradioactive exhaust system will discharge into a newpiping configuration with a volume sufficient to increasethe transit time of the exhaust gas by twenty minutes.This will allow the short-lived radioisotope to partiallydecay before it is discharged to the atmosphere. The newsystem is an FY 1992 Line Item Project. It has beendelayed very nearly a year while additional constructionfunds were requested from DOE. The design criteria havebeen completed, and as soon as the funds are released, thedefinitive design (Title II) will begin. If this happens inthe early fall of 1992, the construction will be completedby November/December 1993.

Radiation Safety Committee Charter

Purpose

The LAMPF Radiation Safety Committee has beenformed to accomplish the following four main tasks:

• Ongoing, continual assessment of the adequacy ofradiation protection systems at LAMPF. At aminimum, the committee will assess readiness beforethe annual start-up and assess effectiveness at the endof each year's operating period.

• Recommend policies and guidelines for radiationprotection at all facilities that use beam from

LAMPF, and provide oversight assessment foroperation at LAMPF. LANSCE, PSR, WNR, andINC at TA-53.Review radiation protection aspects of proposed majorfacility changes and upgrades, including those thatmight impact oth^r occupants at TA-53.Recommend priorities for evaluating and controllingpotential radiation hazards.

Shielding in Service Shafts

Situation

There was concern that in the event of operator,magnet, valve, wire-scanner or interlock failure, acatastrophic beam spill could result, causing excessivelevels of radiation to pass through the 805-MHz wave-guide service shafts to personnel working in the serviceaisle above the beam channel. On April 27, 1990,radiation measurements were made by sending a 758-MeVbeam into a copper bloc\ located in the middle of module46. Results indicated that such a spill would result insignificant radiation levels. Additional radiation measure-ments were conducted using several configurations ofstacked shielding blocks. These measurements alsoindicated that additional shielding would be required.

There are 44 service shafts in the 805-MHt section3.5' x 6' x 26' deep and four shafts in the 201-MHzsection of the linac approximately the same size.

Solution

Several shielding options were considered along withtheir associated cost estimates and manpower require-ments.

One solution appeared to best satisfy the variouscriteria. This option utilized three eight-ft-deep levels ofsand fill in each shaft resulting in a 17,000-lb. load ateach level. All load bearing structures were designed tohave a factor of safety greater than two. The wave guideswere sufficiently stiff to withstand the sand load withoutexcessive deformation. Two thermistors were installed onthe wave guide in different locations to monitor theheating. Cooling provisions were incorporated in theevent that heating was a problem.

The wave-guide service shaft at module 46 was usedas a prototype to develop the shielding installationprocedure and experimentally verify the radiationattenuation.

139

ES&H

Many safety considerations had to be addressed, suchas: head protection, dust masks, safely harnesses, oxygendeficiency, personnel hoists, blowers, burn permits, andbarricades.

During the week of August 27. 1990. the serviceshaft at moduie 46 was filled, and similar radiationmeasurements were conducted on September 2. 1990.Measurements indicated that radiation in the sen ice aislewas reduced to allowable levels. The prototype alsoserved to confirm the cost, duration, manpower, anddevelopment procedures. In addition, it was demonstratedthat the sand could be removed from the shaft in one day.if necessary.

Numerous design details, drawings, safetyconsiderations. Special Work Permits, and QualityAssurance documentation had to be approved and in placebefore work could proceed. Operation of the acceleratorhad to be scheduled around the shielding activities.

Summary

This exercise was important to the operation ofLAMPF. Initially it was felt that only a portion of theshielding job could be completed by the time thatproduction was to star!. The individuals involvedoptimized their procedures, and the shielding in all sen iceshafts was completed in early May.

Considering the scope of the exercise, it wasaccomplished in record time and involved severalindividuals from various organizations with a variety ofdisciplines. The success of the operation illustrates theoutstanding ability and superb interaction of theindividuals involved to accomplish a critical task of thismagnitude on such short notice.

The actual cost of the project was extremely close tothe early estimates. With thorough preparation, and inspite of the difficult working conditions, no injuries orproperty damage were incurred.

Line BR Sweep Magnet

Situation

On May 16. 1991. LAMPF personnel presented aradiation safety assessment of Line X to DOI- atGermantown. This safety assessment recognized that ifone sweep electro-bending magnet failed in the BR LD2pit. the proton beam would transport directlv down the/em-degree neutron production line and interact withtargets and equipment in a lightly shielded experimental

140

cave. Neutron radiation levels would then become highlvunacceptable in occupied areas.

Solution

It was recognized during this safety assessmentpresentation thai a permanent magnet downstream of thesweep electro-bending magnet and upstream of the neutroncollimator would prevent such and accident. A permanentmagnet would still be functional in the event of powerfailures and would not be vulnerable to power supply andcoil faults. Such a magnet had to be in place beforeresearch production could be started in BR. It was hopedto resume research production in late June. No; muchtime was allowed to implement the solution.

A magnet dipole design was produced and thepermanent magnet material was procured through a sole-source vendor. The magnet material could not be shippedby air. Overnight transportation by a special truck wasarranged. Iron for the core w as ordered and draw ings forthe magnet, fixtures, and support structure were produced.

Branch Shop 46. MEC-5. produced the iron core pansand the support structure and magnet assembly fixtureswere fabricated at the ETL shop. Assembly of thepermanent magnet blocks in the core was no minor feat.Each of the 60 permanent magnet elements in the dipolehad an attractive force of approximately 250 pounds.Special assembly fixtures were designed to insert andposition the permanent magnets for bonding in the core.

Magnetic field and integral measurements were madeof one of the magnet sections to verify that the designrequirements were satisfied.

The magnet (made up often sections) and the supportstand were constructed so that they could he installedthrough a 20-inch by 20-inch opening in the shielding toreach the confiricJ space in the beam line.

The dipole was installed on June 27. 1991. and E\p.876 in BR was restored to operation on July 9. 1991.

Summary

This exercise was important to one phase of the

experimental activities at LAMPF. Normally, an activity

of this size could take as long as six months

Considering the scope of the exercise it v.as accomplished

in record lime and involved several individuals from

several groups with a variety of disciplines. The success

of the operation illustrates the outstanding ability and

superb interaction of the individuals involved to

accomplish a critical task of this magnitude on such short

notice.

Accelerator Operations

accelerator Operations

Accelerator operations

David Heifer (Los Alamos)

This report covers operating cycles 59 and 60. Theaccelerator was in operation from June 12 throughAugust 24, 1991. Beams were provided for research usefor 65 days of H+ , 38 days of H~, and 34 days of P~. A

summary of information on beams provided for research isgiven in Table I.

A considerable amount of time was spent in beamloss studies in beam lines to WNR/PSR and the NPL

Table I. Beam Statistics for Cycles 59 and 60.

Cycle 59 Cycle 60Total

Average 1991

Number of experiments served*

H+

H" PSRH- Line XP- Line X

H+

H- PSRH- Line XP- Line X

H+

H" PSRH~ Line XP" Line X

H+H~ PSRH" Line Xp - Line X

scheduled beam (h)scheduled beam (h)scheduled beam (h)scheduled beam (h)

beam availability (%)beam availability (9c)

beam availability (%)beam availability (%)

average current (yA)average current (|iA)average current (jiA)average current (nA)

beam duty factor (9c)beam duty factor (c/r jbeam duty factor (9c)beam dutv factor (c/> \

14 19 33

1128504

226

6335

68

60050

150

6.00.8

608576

592

7565

54

80050

150

6.90.9

!7361080

818

7050

60

70050

150

6.50.85

3.8 3.0 3.4

: Does not include experiments performed at the PSR-LANSCE/WNR areas.

144

Rccelerator Operations

Category

H+ injector systemsH~ injector systems

P~ injector systems

201-MHz rf systems

805-MHz rf systemsVacuum systems

Magnets

Magnet power suppliesInterlock systemsCooling water systems

Computer systems

Production targetsBeam diagnostics

Miscellaneous

TOTAL

Table II. Unscheduled

H+

hours

16.9

90.3

86.9

229.7

8.1

15.27.5

17.7

2.12.6

0.9

47.4

525.3

Machine

%

3.3

17.2

16.543.7

1.5

2.9

1.4

3.4

0.4

0.5

0.2

9.0

100

Downtime During Shifts in 1991.

I-

hours

7.8

46.5

82.553.1

7.8

32.711.514.7

3.7

14.20.0

33.5

308.0

r

%

2.5

15.1

26.817.2

2.5

10.63.7

4.8

1.24.6

0.0

10.9

100

P

hours

54.0

38.8

73.035.5

6.5

11.38.9

17.2

3.9

0.8

0.7

46.0

296.6

-

%

18.2

13.124.6

12.02.2

3.8

3.0

5.8

1.3

0.3

0.2

15.5

100

areas. These studies are part of a continuing effort toanalyze the bulk shielding of areas that carry increasedbeam currents because of advances in technology andadditional facilities. These studies are also beingconducted to evaluate compliance with the LAMPFRadiation Protection Policy.

The cycle 60 bearri schedule ended four weeks early toallow the LAMPF operating groups time to prepare for anextensive DOE Tiger Team audit of LANL.

A summary of unscheduled facility downtime duringresearch shifts is given in Table II. Some of the outagesare concurrent and some affected only one of the threebeams.

A water-to-vacuum leak in a porous copper beamdump in the H+ low-energy transport line was the primarycause for delay of production of all beams by one week.This leak contributed significantly io the vacuum systemsdowntime figure in Table II.

The A-2 target box developed a vacuum leak thatvaried with beam current, actually getting somewhat betterat higher current. The leak also changed during shieldstacking. This leak will require major resources to repair.Increased pumping capacity was added in the interim.Recycling of these additionai cryogenic pumping systemscontributed to the downtime figures for vacuum systems.

This year also showed a significant increase inthunderstorm lightning-induced power outages. LANLwas supplying 13.2-kV systems from the LAMPFsubstation during maintenance of some 115-kVdistribution systems. This supply route is not normallyenergized. A marked reduction in lightning-inducedoutages was noted when this line was first de-energized afew years ago. This line should remain de-energizedduring future summertime production periods.

145

Milestones

Milestones

Milestones

Clinton P. Anderson Meson Physics Facility

1968

Official Ground BreakingSpinoff: Adoption of LAMPF Accelerating Structure for X-Ray Therapy and

Radiography Machines

February 15, 1968

ca 1968

1970

5-MeV Beam AchievedAdoption of a LAMPF Standard Data-Acquisition System

June 10, 1970August 1970

1971

100-MeV Beam Achieved211-MeV Beam Achieved

June 21, 1971August 27, 1971

1972

800-MeV Beam AchievedSpinoff: First Use of Electrosurgical Forceps in Open-Heart Surgery

(University of New Mexico)Discovery of 236Th (Experiment Zero)Dedication to Senator Clinton P. AndersonSpinoff: First Hyperthermic Treatment of Animal Tumors

June 9, 1972

September 13, 1972September 25, 1972September 29, 1972

October 1972

148

Milestones

1973

First H~ Injector BeamFirst Simultaneous H+ and H~ BeamsBeam to Area BFirst Experiment (#56) Received BeamFirst Meson Production, Beam to Area A

March 28, 1973May 4, 1973

July 15, 1973August 24, 1973August 26, 1973

1974

Beam to Area A-EastFirst Medical Radioisotope ShipmentUsable 100-u.A Beam to SwitchyardPi-Mesic Atoms with "Ticklish" NucleiFirst Experimental Pion RadiotherapyFirst Tritium Experiment (80 000 Ci)Start of Great Shutdown

February 6, 1974July 30, 1974

September 5, 1974October 13, 1974October 21, 1974November 1974

December 24, 1974

1975

New Precise Measurements of Muonium Hyperfine Structure Interval andji+ Magnetic Moment

Q Data-Acquisition Software OperationalSpinoff: First Use of 82Rb for Myocardial Imaging in Humans (Donner Lab,

Lawrence Berkeley National Laboratory)Spinoff: First Hyperthermic Treatment of Human Cancer (University of

New Mexico)Accelerator Turn OnAcceptable Simultaneous 100-jxA H+ and 3-(xA H~ Beams to SwitchyardProduction Beam to Area B

1975-77-80June 1975

June 1975

July 11, 1975August 1, 1975

September 14, 1975October 7, 1975

1976

First Pions Through EPICSProduction Beam in Areas A and A-East: End of Great ShutdownMuon-Spin-Relaxation ProgramSpinoff: First Hyperthermic Treatment of Cancer Eye in Cattle

(Jicarilla Reservation)100-uA Production Beam in Area AExperiment in Atomic Physics (H~ + laser beam): Observation of Feshbach and

Shape Resonances in H~Double Charge Exchange in 16O: LEP ChannelStartup of Isotope Production Facility

March 18, 1976April 5, 1976

June 1976

June 3, 1976August 1976

October 1976October 5, 1976

October 15, 1976

149

Milestones

1976 (continued)

HRS Operation BeginsMaintenance by "Monitor" System of Remote Handling

November 1976Fall 1976

1977

Proton Beam to WNRPolarized-Proton Beam AvailableSpinoff: First Practical-Applications Patent Licensed to Private IndustryPion Radiotherapy with Curative IntentProton-Computed Tomography ProgramExperimental Results at Neutrino FacilityCloud and Surface Muon Beams: SMCEPICS Operation Begins300-(iA Production Beam in Area A

March 12, 1977April 1977

April 12, 1977May 1977June 1977July 1977July 1977

August 1977Fall 1977

1978

AT Division EstablishedTfi Spectrometer Begins OperationOperation of Polarized-Proton TargetSuccessful Water-Cooled Graphite Production Target

January 1, 1978February 1978

Spring 1978November 1978

1979

Spinoff: First Thermal Modification of Human Cornea (University ofOklahoma)

600-u.A Production Beam in Area ANew Limit on fi -> ey

July 11, 1979November 1979December 1979

1980

Experimental Measurement of the Strong-Interaction Shift in the 2p-1 sTransition for Pionic Hydrogen

Commercial Production of RadioisotopesSpin Precessor Begins OperationData-Analysis Center OperationalVariable-Energy OperationSingle-Isobaric-Analog States in Heavy NucleiSpinoff: First Use of 82Rb for Brain Tumor Imaging in Humans

(Donner Lab, Lawrence Berkeley Laboratory)

1980-81-82January 1980

February 1980April 1980June 1980June 1980

September 1980

150

Milestones

1980 (continued)

Production of Fast Muonium in Vacuum Fall ] 980Double-Isobaric-Analog States in Heavy Nuclei October 1980Focal-Plane Polarimeter Operational at HRS October 1980Safety Award to LAMPF Users Group, Inc., for Working One Million

Man-Hours Since 1975 Without a Disabling Injury October 27, 1980New Measurement of Pion Beta Decay - Improved Test of Conserved-Vector

Current November 1980

1981

First Excitation of Giant Dipole Resonance by Pion Single Charge Exchange March 1981First Observation of Iso vector Monopole Resonance in 120Sn and 90Zr by Pion

Single Charge Exchange March 1981Negative Evidence for Critical Opalescence in 40Ca September 1981

1982

Average Beam Current of LAMPF Accelerator Established at 750 JJA 1982Staging Area Constructed 1982"Dial-a-Spin" Capability on Line B Permits Different Spin Orientations for

HRS, Line B, and EPB Simultaneously 1982Improved Test of Time-Reversal Invariance in Strong Interactions by

Comparison of the Polarization in the Reaction pd -» n pp withthe Analyzing Power in the Interaction np —> pn 1982

dt Fusion Catalyzed by Muons November 1982

1983

LAMPF Accelerator Produces Proton Beam of 1.2 mA February 7, 1983First Observation of ve-e~ Scattering October 1983Result for Asymmetry in p p Scattering Caused by Parity

Violation: AL = (2.4 ± 1.1) x 10"7 at 800 MeV November 1983

1984

Duty Factor > 9% Achieved February 1984Total Cross Section for ve-e~ Scattering oT = lO"44} Ev (GeV) cm2 May 1984Clamshell Spectrometer On Line June 1984High-Intensity H~ Source Operational September 1984

LSI

Milestones

1985

New Beam Stop Installed by Remote-Handling System Spring 1985High-Intensity H~ Injector Operational April 1985New Switchyard Permits Three-Beam Operation April 1985Proton Beam to Proton Storage Ring (PSR) May 1985Routine Production at Beam Current of 1 mA Summer 1985Precise Near-Threshold Measurements of irp JE 7t°n Reaction July 1985T]-Meson Production on Nuclei Observed Near Threshold August 198517-mA Peak Current Achieved September 1985Precise Test of the Relativistic Doppler Effect at 0.84c by Collision of an

Atomic Beam with Laser Light 1985

1986

Verification of Destructive Interference Between the Charged-Weak andNeutral-Weak Amplitudes in ve Scattering (Exp. 225) 1986

Group MP-5 Formed to Maintain and Develop Line D and theProton Storage Ring 1986

Masses of 12 New Isotopes Measured by TOFI System 1986Polarized Beam Delivered with 10-MHz Micropulse Structure for Neutron Timing 1986

1987

Neutron Time-of-Flight Facility Short-Flight-Path Commissioned(New Beam Line in NPL) ] 987

Linac Rebuncher Scheme Implemented to Produce Time-Focused Micropulses atWNRandNTOF 1987

113-MeV Beam Delivered to WNR/Lowest Energy Delivered by LAMPF to anExperimental Area 1987

Operation with Three Beam Energies to Line A, Line D, and Line X 1987Development of Medium-Resolution (0.2%) Tune for P3 1987

1988

Polarized Nuclear Target used in Research (13C on HRS for Exp. 955) 1988CYGNUS Experiment (uses LAMPF Neutrino Detectors) Publishes Results

on Muon Excess from Ultra-High-Energy Cosmic Ray Showers 1988

152

Milestones

1989

Pion Scattering from Polarized 13C May 1989Commissioned MRS Achieving 1.3-MeV Resolution at 800 MeV July 1989Quantitative Verification of Standard Model through Neutrino Electron Scattering

(Exp. 225) 1989Large Role of Two-Nucleon Correlations Demonstrated for DCX Reactions

on Ca Isotopes 1989Limits Established from y^ —> Ye Oscillations (Exp. 645) 1989First Polarized Beam to Experimental Area from OPPIS 1989Completion of Measurement of All I = 1 Amplitudes in p-p Scattering

up to 800 MeV 1989

1990

Measurement of Parity Violation in Compound Nucleus Resonances in n + 238UReactions using Pulsed Neutrons from LANSCE 1990

Utilization of a Polarized 13C Target for Proton and Pion Elastic and InelasticScattering Studies 1990

First Complete Determination of Spin Transfer Observables using (n , n) Reactionsin D and Pb at NTOF 1990

Production of Best Upper Limit for Conversion of Muonium to Antimuonium 1990Use of H~ Beam to Provide First Observations of Multiphoton Detachment of H° 1990First Demonstration of Optical Pumping Technique for Making Polarized Muonic

Atoms using Charge Exchange and Spin Exchange of a\i~ with Rb 1990OPPIS, the Optically Pumped Polarized Ion Source, Exceeded the Goals for

Current (25 (lA) and Polarization (55%). Readability Exceeded 90% 1990Parity Violation in 238U Observed using Pulsed Neutrons from LANSCE 1990

1991

Scruncher Cavity Exceeds 8 MV/m at Q > 109 after Chemical Cleaning inLos Alamos Clean Room 1991

NMS Prototype Csl (pure) Large Volume Calorimeter Crystals Give <1 % EnergyResolution with Photon Beams Produced in P3 Channel 1991

The Optically Pumped Polarized Ion Source (OPPIS) Provided 38 |lA of Beamwith Polarization of 0.64 and Overall Source Availability of 90% 1991

Polarized !3C Target used with EPICS for Elastic and Inelastic AsymmetryMeasurements 1991

First NTOF Polarization Data Consisting of Complete Set of PolarizationTransfer Observables for Quasi-Free Reactions 1991

Improvement in Statistical Weight by at Least 100 Times Over Previous Data forPolarization Transfer Observables in np Scattering 1991

Pion DCX on ' 'B Target Producing Neutron-Rich Exotic Nucleus "Li 1991

153

Milestones

1991 (continued)

Establishment of an Asymmetry in the Sign of Interference Term in Parity-ViolatingNeutron-Nucleus Resonances 1991

Most Stringent Limits on Neutrino Properties Outside the Standard Model; MagneticMoment, Charge Radius, Flavor-Changing Neutral Currents, andNeutrino Decay 1991

154

Appendixes

EXPERIMENTS RUN IN 1991

NEW PROPOSALS DURING 1991

LAMPF VISITORS DURING 1991

HppendiK flEHperiments Run in 1991

APPENDIX A:Experiments run in 1991

Exp.No.

267

876

1017

1026

1054

1079

1100

1107

1133

1139

1140

1179

1190

Channel

IP

BR

EPICS

P3

SMC

HRS

TOFI

P3

HRS

HRS

P1

LEP

P3

BeamHours

1200

186

451

341

25

77

921

21

486

120

248

288

267

Title

Preparation of Radioisotopes for Medicine and the Physical SciencesUsing the LAMPF Isotope Production Facility

Spin Transfer Measurements for NP Elastic

Interference Effects in Nonanalog Pion Double Charge Exchange

A Study of the 3H(7t+,7i°)3He Reaction

Ultra High Precision Measurements on Muonium Ground State:Hyperfine Structure and Muon Magnetic Moment

Development of Experimental Techniques to Study RelativisticEffects in Proton-Nucleus Elastic Scattering at Forward Angles

Mass Measurements of Neutron-Rich Nuclei with Z = 18-32

Studies of Pion Double Charge Exchange Scattering at Energiesabove the A Resonance

Inelastic Proton Scattering from I82,i84\y a n d the IBA Model

Testing of Radiation Resistance of Read-Out Chips for Use in High-Rate Nuclear and Particle Physics Applications

Search for r|° Component in Pion DCX

Reaction n+p —> 7i+7i°p Near Threshold

Pion-Proton Transmission Cross Section Measurements

158

Exp.No. Channel

BeamHours Title

HPPENDIK HExperiments Run in 1991

1191

1198

1207

1210

1212

1223

1231

1234

1235

EPICS

LEP

EPICS

LEP

SMC

EPICS

SMC

BR

SMC

122

426

259

277

270

88

386

127

225

Excited States of a Neutron-Rich Nucleus "Li via Pion DCXReaction

Correlation Effects in Analog DCX on Nickel Isotopes

The Nature of T< States Observed in DCX on Medium Mass Nuclei

Study of the Mechanism for DCX to Excite Analogs of Anti-Analogs in Heavy Nuclei

Nuclear Charge Radii in the Strongly Deformed Region 66Dy to74W by Muonic Atoms

Narrow Structure Above the Double Resonance Region in DoubleCharge Exchange

Laser Polarized Muonic Atoms and Spin Dependence of NuclearMuon Capture

KLL and P for np Elastic Scattering

: Level-Crossing Resonance Spectroscopy

159

RppendiH BNew Proposals During 1991

APPENDIX B:New proposals during 1991

Exp.No. Spokespersons Title

1213 K. LandeUniv. of Pennsylvania

1214 J. M. O'DonnellLos Alamos

1215 K. S. DhugaGeorge Washington Univ.

W. J. BriscoeGeorge Washington Univ.

1216 D. K. DehnhardUniv. of Minnesota

J. L. LangenbrunnerUniv. of Minnesota

M. K.JonesRutgers Univ.

1217 C.F.MooreUniv. of Texas, Austin

S. MordechaiBen-Gurion Univ.

1218 H. C. BryantUniv. of New Mexico

J. B. DonahueLos Alamos

Measurement of the Neutrino Capture Cross Section in 37C1and l27I with j.i+ Decay Neutrinos

The 0+ Strength to the GDR2

Pion Single Charge Exchange on the A = 3 Nuclei

6Li(jt,7i'X) Coincidence Measurements Near the A33Resonance

Accurate Determination of the T> Giant Dipole State in LightT = 1/2 Nuclei Using Pion DCX

Branching Ratios and High Resolution Spectroscopy of theDoubly-Excited Hydrogen Ion

160

HPPENDIX BNem Proposals During 1991


1219 B. BrinkmdlierUniv. of Karlsruhe

C. M. RiedelUniv. of Minnesota

D. K. DehnhardUniv. of Minnesota

1220 B. BrinkmollerUniv. of Karlsruhe

E. BoschitzUniv. of Karlsruhe

1221 H. T. FortuneUniv. of Pennsylvania

M. McKinzieUniv. of Pennsylvania


M. McKinzieUniv. of Pennsylvania



P. HuiUniv. of Pennsylvania


1226 B.G.RitchieArizona State Univ.

1227 B.G.RitchieArizona State Univ.

1228 D. R. BentonUniv. of Pennsylvania

H. T. FortuneUniv. of Pennsylvania

Elastic Scattering of 7C+ and IT from 4He and 3He Above theA3.3 Resonance

Measurement of Angular Distributions dc/dQ for 6Li(rt+,7t+)at TK = 100 MeV, 134 MeV, 164 MeV, 190 MeV, and219 MeV

The Analog Double Charge Exchange Reaction on a Mid-Shell T=l Nucleus

Nonanalog Double Charge Exchange Transitions to Low-Lying Excited States via 27Al(7r,7i+)27Na

Narrow Structure Above the Double Resonance Region inDouble Charge Exchange

Measurements of DCX Ground State Cross Sections for SeIsotopes at TK = 164 MeV

Low-Energy Pion Double Charge Exchange on Se Isotopes

A Study of the Pion-Nucleus Isovector Spin-FlipMechanism at Low Energies Using 1()B

The Two-Proton Component of the Pion AbsorptionReaction on Nuclei at Low Energies

Nonanalog Double Charge Exchange on Nickel Isotopes

Rppendix BNew Proposals During 1991

SpokespersonsExp.No. Title


M. A. KagarlisUniv. of Pennsylvania

1230 R. GilmanRutgers Univ.

1231 G. D. CatesPrinceton Univ.

P. A. SouderSyracuse Univ.

1233 D. A. SmithUniv. of Pennsylvania


1234 M. McNaughtonLos Alamos

1235 M.LeonLos Alamos

W. CookeLos Alamos

1236 D. R. BentonUniv. of Pennsylvania


1237 M. S. LubellCity College of CUNY, NY


1239 C. L. MorrisLos Alamos

M. W. Rawool-SullivanNew Mexico State Univ.

P. SiegelCalifornia Polytechnic Inst.

Search for Sequential DCX to the Ground State

.TT) at D33 Resonance Energies

Laser Polarized Muonic Atoms and Spin Dependence ofNuclear Muon Capture

Double Giant Resonances Involving the IVM

and P for np Elastic Scattering

jiSR: Level-Crossing Resonance Spectroscopy

The T = 2 Anomaly and Double Charge Exchange on

Precision Measurement of the Threshold Behavior of DoublePhotodetachment of the Negative Hydrogen Ion

A DCX Experiment to Isolate the A,B Amplitudes of theSeniority Model

Feasibility of the Direct Production of Pionic Atoms atLAMPF

162

RPPENDIXBNew Proposals During 1991


1240 M. D. CooperLos Alamos

R. E. MischkeLos Alamos

1241 C. F. MooreUniv. of Texas, Austin


1242 C. F. MooreUniv. of Texas, Austin




M. A. KagarlisUniv. of Pennsylvania










J. O'DonnellLos Alamos

A Proposal to Measure the Michel Parameter Rho with theMEGA Positron Spectrometer

Isospin Structure of the Giant Dipole Resonance in PionSingle Charge Exchange

The Double Giant Dipole Resonance in Deformed Nuclei

Population of T< Configuration States in Double ChargeExchange

Search for the Signature of Spin-Flip and Sequential DCX tothe Ground State

Pion DCX on Odd Z Nuclei, an Experiment to ClarifyApparent Shell Effects in DIAS Cross Sections

Comparisons of the GDR Widths in 139La and 165Ho

Nonanalog Double Charge Exchange on

Nonanalog Single Charge Exchange on I6O

An Experiment to Calibrate Spin-Flip Contributions to DCX

163

Rppendix BNew Proposals During 1991

SpokespersonsExp.No. Title

1250 D. P. BeattyRutgers Univ.

R. GilmanRutgers Univ.


S. LoeUniv. of Pennsylvania

1252 A.L.WilliamsUniv. of Texas


1253 C.L.MorrisLos Alamos

R. J. PetersonUniv. of Colorado

1254 C.L.MorrisLos Alamos

R. J. PetersonUniv. of Colorado

1255 G. GlassTexas A&M Univ.

T. ShimaTexas A&M Univ.

1256 G. R. BurlesonNew Mexico State Univ.

J. R. ComfortArizona State Univ.

1257 J. M. WoutersLos Alamos

W. TalbertLos Alamos

Interference Effects in Nonanalog Double Charge Exchange

Narrow Structure in Double Resonances in ' - '

Isospin Nature of High Energy Pion Double ChargeExchange

Giant Resonance Excitations by Low Energy PionScattering

Isobaric Analog Transitions from the (Jt,r|) Reaction (P3)

Studies of AN in p + p —> K+ + X Inclusive Reactions

n* p Analyzing Powers at 45 and 67 MeV

Operation of a He-Jet System at High Beam Intensity andStudies of Neutron-Rich Fission Products in the A = 100-120 Region, and Electromagnetic Moments for RefractoryElements

164

RPPENDIXC

APPENDIX C:LAMPF visitors during 1991

LHMPF Uisitors During 1991

David Adams. Rice Univ.. USAHyo Ahn, Yale Univ., USAMichael Albert. Univ. of Pennsylvania, USADimitris Alexandreas, Univ. of California. Irvine, USAGlenn Allen, Univ. of Maryland, USAChris Allgower. Arizona State Univ.. USADavid Ambrose, Univ. of Texas at Austin, USAPal Apai. Univ. of New Mexico, USAJoffa Applegate, Arizona State Univ., USAJeff Arrington. Abilene Christian Univ., USAKetevi Assamagan. Univ. of Virginia. USAChristos Athanassopoulos, Temple Univ., USALeonard Auerbach, Temple Univ., USANaftali Auerbach. Tel-Aviv Univ.. IsraelPeter Barnes, Los Alamos National Laboratory, USAAmy Barton. Princeton Univ., USASteven Barwick, Univ. of California. Irvine, USADavid Beatty, Rutgers Univ., USAJames Beck. Arizona State Univ., USAMichael Beddo. Argonne National Laboratory. USAVladimir Bekrenev. Leningrad Nuclear Physics

Laboratory, RussiaHan Ben-Zvi. Brookhaven National Laboratory, USADonald Benton. Univ. of Pennsylvania, USADavid Berley. National Science Foundation, USACarsten Bernhardt. Institut fiir Kernphysik, GermanyMartin Berz, Michigan State Univ.. USAHans Bethe, Cornell Univ.. USASteven Biller, Univ. of California, Irvine. USALouis Bimbot. IPN Orsay. FranceDieter Bloess, CERN. SwitzerlandCarolus Boekema. San Jose Stale Univ.. USAPaul Bogorad. Princeton Univ.. USAJeffrey Brack, TRIUMF. CanadaGerald Brady. Univ. of Pennsylvania, USAHerbert Breuer. Univ. of Maryland. USAWilliam Briscoe. George Washington Univ., USA

Tyson Browning, Abilene Christian Univ., USAHoward Bryant, Univ. of New Mexico, USAJames Buchanan, Rice Univ.. USAGeorge Burleson, New Mexico State Univ., USAPeter Busch, Univ. of Toronto, CanadaJohn Calhoun, Rice Univ., USAJohn Cameron, Indiana Univ., USARebecca Caress, George Washington Univ., USAJohan Carlson, Manne Siegbahn Institute of Physics,

SwedenJames Carr, Florida State Univ., USAHamilton Carter, Ohio State Univ., USAGordon Cates, Princeton Univ., USAMatteo Cavalli-Sforza, Univ. of California, Santa Cruz,

USASoumya Chakravarti, California State Polytechnic

Institute, USATed Chang, Los Alamos National Laboratory. USANicholas Chant, Univ. of Maryland, USAChing Min Jasson Chen, Texas A&M Univ., USAJiaer Chen, Peking Univ., PRCJian-Ping Chen, Univ. of Virginia. USAMarc Chen, California Institute of Technology, USASiyu Chen, National Natural Science Foundation, PRCXiao-Yan Chen, Univ. of Colorado. USACheewee Chew, Univ. of Pennsylvania, USASong Hun Choi, Arizona State Univ., USALeonard Christofek, Virginia Tech, USADouglas Ciskowski. Yale Univ., USAFrancis Close. Univ. of Tennessee. USAWilliam Coffey, Univ. of Texas at Austin. USAira Cohen, Linfield College, USAJoseph Comfort, Arizona State Univ., USADeborah Cook, Nonaffiliated, USAPeter Cooper, Fermi lab. USASteven Corbato, Univ. of Utah, USAJack Cossairt, Fermilab, USA

165

BPPENDIHCLflMPF Visitors During 1991

Larry Coulsan. Superconducting Super Collider. USASteven Cox. Rutherford Appleton Laboratory. UKGerard Crawley. Michigan State Univ.. USAKen Crook. Stanford Univ.. USAPaul Czarapata. Fermilab, USAHerbert Daniel. Technische Universitiit Miinehen.

GermanyCharles Davis. TRIUMF. CanadaJohn Davis, Univ. of New Mexico. USANorman Davison. Univ. of Manitoba. CanadaW. Dawson. TRIUMF. CanadaAnthony Day, Norfolk State Univ.. USAJoseph De Grande, Lawrence Livermore National

Laboratory. USAR. DeLay. Univ. of California. Irvine. USADietrich Dehnhard. Univ. of Minnesota. USASteven Delucia. Ohio State Univ., USASatish Dhawan. Yale Univ.. USAKalvir Dhuga. George Washington Univ.. USAThomas Dickinson. Brookhaven National Laboratory.

USAWolfgang Diete. Univ. of Wuppertal. GermanyByron Dieterle. Univ. of New Mexico, USADimitrios Dimitroyannis. Northwestern Univ.. USACynthia Dion, Univ. of Maryland. USAGerard Dion. Univ. of California. Irvine, USAJay Dittmann. Valparaiso Univ.. USAGail Dodge. Stanford Univ.. USAWilliam Dodge. George Washington Univ., USAMaria Dowell. MIT, USASinisa Dragic. George Washington Univ.. USAJuergen Duppich. Paul Scherrer Institute. SwitzerlandMario Dzemidzic. Univ. of Houston. USAGordon Eaton, Rutherford Appleton Laboratory, UKGeoffrey Edwards, Rutgers Univ., USAAlan Eisner. SLAC. USAMaher El-Ghossain. New Mexico State Univ.. USAPaul Ellis. Univ. of Minnesota. USAJohn Ellison. Univ. of California. Riverside. USARobert Ellsworth. George Mason Univ.. USAKeith Elmore. Abilene Christian Univ.. USACharlotte Elster. Ohio State Univ.. USAHandjoerg Emrich. Hessisches Minisgterium F. Umwelt

Univ.. GermanyPeter Englert. San Jose State Univ.. USADavid Ernst. Texas A&M Univ.. USAMichelle Espy. Univ. of Minnesota. USAThomas Estle. Rice Univ., USARoy Faulkner. Institute of Polymer Technology and

Materials. UKAli Fazely, Southern Univ.. USAFred Federspiel, Los Alamos National Laboratory. USAXiang Fei, Yale Univ.. USAKenneth Fertner. Advanced Technology Labs. USALeslie Fifield. Australian National Univ.. Australia

Sergei Filippov. Institute for Nuclear Research. RussiaBenjamin Finle.i Univ. of Maryland. USAJohan Flick. Univ. of Houston, USAWilson Fong. MIT. USAH. Fortune. Univ. of Pennsylvania. USATom Francke. Centre des Recherches Nucleaires. FranceMichael Franey, Univ. of Minnesota. USAStuart Freedman. Univ. of California. Berkeley. USAGerhard Fricke. Univ. of Mainz. GermanyJonathan Friedman, City College of New York. USAEmil Frlez. Univ. of Virginia. USASaihong Fu. Institute of Atomic Energy. PRCHerbert Funsten, College of William & Mary. USACarl Gagliardi, Texas A&M Univ.. USAIan Gardner. Rutherford Appleton Laboratory, UKScott Garner. Abilene Christian Univ., USAHenry Garrett. Lawrence Livermore National Laboratory.

USAJurij Gavrilov. Institute for Nuclear Research. RussiaVladimir Gavrin, Institute for Nuclear Research, RussiaHartmut Gemmekke. Kemforschungszentgrum Karlsruhe,

GermanyRobert Giannelli. Univ. of New Mexico. USAEdward Gibson. California State Univ.. Sacramento. USARonald Oilman. Rutgers Univ., USACamille Ginsburg. Northwestern Univ.. USACharles Glashausser. Rutgers Univ., USAGeorge Glass. Texas A&M Univ.. USAJason Glenn, Univ. of New Mexico, USASandra Gomulka, Univ. of New Mexico. USACharles Goodman, Indiana Univ.. USAJordan Goodman. Univ. of Maryland. USAChristopher Gould. North Carolina State Univ.. USAJean-Pierre Gourber, Centre European Organization for

Nuclear. SwitzerlandMikhail Grachev. Academy of Sciences. RussiaHand-Dieter Graef. Technische Hochschule Darmstadt.

GermanyAndrew Green. Rutgers Univ.. USAChilton Gregory, Univ. of New Mexico. USAThomas Gresko. Univ. of Virginia. USAFedor Guber. Institute for Nuclear Research. RussiaGilbert Guignard, CERN, SwitzerlandErhan Giilmez. Univ. of California. Los Angeles. USADavid Haase, North Carolina State Univ.. USADavid Hahn, Northwestern Univ.. USAQuamrul Haider. Fordham Univ.. USARonald Haigh Lawrence Livennore National Laboratory,

USA

Todd Haines. Univ. of Maryland, USAMonica Halka. Univ. of New Mexico. USAStanley Hanna. Stanford Univ.. USAJohn Harris. Stanford Univ.. USATomoyuki Hasegawa. Univ. of Tokyo, JapanOsamu Hashimoto. Univ. of Tokyo. Japan

166

RPPENDIX C

Ferenc Hegedus. Paul Scherrer Institute. SwitzerlandHorst Heinrichs. Univ of Wuppertal. GermanyMaris-Claude Henkel. Technische Hochschule

Darmstadt. GermanyWalter Hensiey. Battelle Pacific Northwest Lab.. USAPhilip Hermidu. Temple Univ.. USAWilhemus Hesselink. Free Univ. of Amsterdam.

The NetherlandsGary Hiatt. Westinghouse Electric Corporation. USAJohn Hiebert. Texas A&M Univ.. USAVirgil Highland. Temple Univ.. USABassam Hitti. Rice Univ.. USAA in in Hoffart. Universitat Karlsruhe. GermanyGerald Hoffmann. Univ. of Texas at Austin. USASteinar Hoibraten. Univ. of Colorado. USAMichael Holcomb. Univ. of Colorado. USAKarl Holinde. Univ. of Bonn. GermanyRichard Holmes. Syracuse Univ.. USABas Den Hond. TROUW. The NetherlandsDaniel Horen. Oak Ridge National Laboratory. USARoger Home. CERN. SwitzerlandPaul Huffman. Duke Univ.. USAKeith Hugenberg. Lawrence Livermore National

Laboratory, USAPatrick Hui. Univ. of Pennsylvania, USAEd Hungerford. Univ. of Houston, USAAhmed Hussein. King Fahd Univ. of Petroleum and

Minerals. Saudi ArabiaFrancofonte Iachello. Yale Univ.. USANaoki Igawa. Japan Atomic Energy Research Institute,

JapanRichard linlay. Louisiana State Univ., USATaku Ishida. Institute for Cosmic Ray Research. JapanRex Evie. Univ. of Pennsylvania. USAHarold Jackson. Argonne National Laboratory. USARobert Jaffe. MIT. USAHubert Jager. Darmstadt Institiit fur Kerphysik. GermanyMuhammad Jahan. Memphis State Univ.. USACvjetan Jakovljevic. Technoloskj Fakullet. YugoslaviaRandolph Jeppesen. Univ. of Montana. USASteve Jerger. Univ. of California. Riverside. USAWenmian Jiang. Institute of Nuclear Physics and

Chemistry. PRCBernhard Jobst. Univ. of Texas at Austin. USAJohn Johnson. Univ. of Texas at Austin. USAKeven Johnson. Univ. of Texas at Austin, USAKathleen Johnston. Los Alamos National Laboratory,

USAMark Jones. Rutgers Univ.. USARobert Jones. New Mexico State Univ.. USADavid Joyce. Univ. of California, Riverside. USACharles Jui. Stanford Univ.. USARoland Jung. CERN. SwitzerlandMarios Kagarlis. Univ. of Pennsylvania. USAGeorge Kahrimanis. NonaffiliaLed. USA

LflMPF Uisitors During 1991

Takaaki Kajita. Institute for Cosmic Ray Research. JapanPeter Karen. Univ. of Virginia. USAJoachim Kastner. Univ. of New Mexico. USAKara Keeter. Univ. of Virginia. USALinda Kelley. Univ. of California. Santa Cruz. USAMichael Kelly. Univ. of Virginia. USARobert Kenefick. Texas A&M Univ.. USAMahbubul Khandaker. Univ. of Maryland. USAMohammad Khayat. Univ. of Maryland. USAGrant Kiehne. Valparaiso Univ.. USAWilliam Kielhorn. Univ. of Texas at Austin, USAGeorge Kim. Texas A&M Univ.. USABruce King. Stanford Univ.. USAEdward Kinney. Univ. of Colorado. USALeonard Kisslinger. Carnegie-Mellon Univ.. USAPamela Klabbers, Univ. of California. Irvine. USAAndres Klein. Old Dominion Univ.. USASpencer Klein. Univ. of California. Santa Cruz. USAVictor Klenov. Academy of Sciences, RussiaPeter Kneisel. Continuous Electron Beam Accelerator

Facility. USATakenori Kobayashi, Rensselaer Polytechnic Institute.

USAToshio Kobayashi. KEK, JapanDonald Koetke. Valparaiso Univ.. USAMatthew Kohler. Univ. of Colorado. USAYutaka Kohno. Univ. of Tokyo, JapanAkira Kohyama. Univ. of Tokyo, JapanChris Kormanyos, Univ. of Colorado. USAJames Koster, Los Alamos National Laboratory. USAYoshihisa Kotooka. Hammamatsu Corporation. JapanJoseph Kowalczyk. Los Alamos National Laboratory.

USAHeribert Koziol. CERN, SwitzerlandJack Kraushaar. Univ. of Colorado, USAFrank Krawczyk, Technische Hochschule Darmstadt.

GermanyBrian Kriss, Univ. of Colorado, USAAlexei Kurepin. Institute for Nuclear Research. RussiaTanya Kurosky. Univ. of California. Santa Cruz. USADenis L'Hote. CEN-Saclay. FranceJose Labanda, Northwestern Univ.. USAJohn Lam, San Jose Stale Univ., USAC. Lamp. Texas Tech Univ., USAMayer Landau. Univ. of Pennsylvania. USAKenneth Lande. Univ. of Pennsylvania. USAJames Langenbrunner. Univ. of Minnesota. USABart Larson. Simon Fraser Univ., CanadaSamuel Larson, Iowa State Univ.. USASieven Lassiter. Continuous Election Beam Accelerator

Facility. USAPhilippe Lebrun. CERN. SwitzerlandAlwin Lehniann. Institut fur PhysiK der Untveisitat Basel.

SwitzerlandRenzo Leonardi. Universita di Trento. Italv

167

RPPENDIHCLHMPF Uisitors During 1991

Mark Lesko. Univ. of Virginia. USAZenghai Li. Institute of Atomic Energy. PRCRoger Lichti. Texas Tech Univ.. USAChristopher Lietzke. Univ. of California. Riverside.

USAVladimir Litvinenko. Duke Univ.. USAFan Liu. Texas A&M Univ.. USADonald Lobb. Univ. of Victoria. CanadaVincent Lodestro. Brookhaven National Laboratory. USAGreg Loe. Abilene Christian Univ.. USAStephen Loe. Univ. of Pennsylvania. USABenoit Loiseau. Univ. of Paris IV. FranceEarle Lomon, MIT. USAJ. Londergan. Indiana Univ.. USAJoshua Long. Johns Hopkins Univ.. USAIgor Lopatin. Leningrad Nuclear Physics Institute. RussiaWilliam Love. Univ. of Georgia. USAMark Lowry. Lawrence Livermore National Laboratory.

USAAdolph Lu. Univ. of California, Santa Barbara. USAMichael Lubell. City Univ. of New York, USAAnthony Lucas. Micron Semiconductor, USAYixiao Luo, Institute for Modern Physics. PRCBryan Luther, Ohio State Univ.. USAHideo Mabuchi. Princeton Univ.. USAMalcolm MacFarlane. Indiana Univ.. USAEdward MacKerrow. Univ. of New .Mexico. USAAlfred Mann. Univ. of Pennsylvania. USAAneesh Manohar. MIT. USARobert Manweiler. Valparaiso Univ.. USANaifeng Mao, Los Alamos National Laboratory. USADonald Marchlenski. Ohio State Univ.. USAGurey Marchuk. Soviet Academy of Sciences. RussiaDemetrius Margaziotis, California State Univ..

Los Angeles. USARichard Marshall. Univ. of Virginia. USAWilliam Marterer. Nonaffiliated. USAJohn Matthews. Johns Hopkins Univ.. USAJune Matthews. MIT. USAScott Matthews. George Washington Univ.. USABjorn Matthias. Physii._!;:.c!.cs Institiit. GermanyVictor Matveev. Institute of Nuclear Research. RussiaSiun Mau. Univ. of Pennsylvania. USABill Mayes II. Univ. of Houston. USAPeter Mazanek. Institiit fur Kernphysik. GermanyKert McCammon. Lawrence Livennnre National

Laboratory. USAJames McCarthy. Univ. of Virginia. USADorothy McCracken. Syracuse Univ.. USAMatthew McKinzie. Univ. of Pennsylvania. USARobert McLeod. Idaho State Univ.. USAGary JVIcMills. Louisiana State Univ.. USAKok-Heong McNaughfon. Univ. of Texas at Austin. USABernhard Mecking. Continuous Electron Beam

Accelerator Facility. USA

David Mercer. Univ. of Colorado. USAMartin Merck. Max-Planck-Institiit fur Physik. GermanyChristoph Mertz. Arizona State Univ.. USAWilliam Metcalf. Louisiana State Univ.. USAHans Meyer. Indiana Univ.. USAHunter Middleton. Princeton Univ.. USADimitris Mihailidis. Univ. of Minnesota. USAMikhail Mikheev. Institute for High Energy Physics.

RussiaKenneth Milano. United States Naval Academy. USAHarry Miley, Battelle Pacific Northwest Lab.. USADavid Millener. Brookhaven National Laboratory. USAC. Miller. TRIUMF. CanadaWilliam Miller. Univ. of New Mexico. USARalph Minehart. Univ. of Virginia. USAGary Mitchell. North Carolina State Univ.. USAJoseph Mitchell. Univ. of Virginia, USAMotoharu Mizumoto. Japan Atomic Energy Research

Institute. JapanAmir Mohagheghi. Nonaffiliated. USAC. Fred Moore, Univ. of Texas at Austin, USAShaul Mordechai. Ben-Gurion Univ.. IsraelAnny Morrobel-Sosa. California State Polytechnic.

San Luis Obispo. USASanjoy Mukhopadhyay. Nova Electronics and Software.

USAHirohiko Murata. Japan Atomic Energy Reserach

Institute, JapanTakeo Muroga, Kyushu Univ.. JapanStephen Musolino. Brookhaven National Laboratory.

USAKoji Nakai, KEK, JapanSirish Nanda. Continuous Electron Beam Accelerator

Facility. USAJames Napolitano, Continuous Electron Beam

Accelerator Facility. USAMinoru Narui. Tohoku Univ.. JapanNathan Newbury. Princeton Univ.. USAThomas Nichols. Univ. of New Mexico, USAMichael Nitschke. Lawrence Berkeley Laboratory. USABlaine Norum. Uni i. of Virginia. USAKeran O'Brien. Northern Arizona Univ.. USAKamo Oganesyan. Joint Institute for Nuclear Research.

RussiaChihiro Ohmori. Univ. of Tokyo. JapanJean Oostens. Univ. of Cincinnati. USAMichael Osterlund. Univ. of Lund. SwedenJulie Ostranderr. Saginaw Valley State Univ.. USAPeter Ostroumov. Institute for Nuclear Research. RussiaShelly Page. Univ. of Manitoba. CanadaMichal Palarczyk. Unix, of Minnesota. USAAndrea Paiounek. Univ. of New Mexico. USAVladislov Pantuev. Institute for Nuclear Research. RussiaHojoon Park, MIT. USASteve Parry. Univ. of Colorado. USA

168

RPPENDIXC

Evgueni Pasyuk. Joint Insiitute for Nuclear Research.Russia

Sharon Patterson. North Carolina State Univ.. USAPhillip Patton. Univ. of Georgia, USAThomas Paul. Johns Hopkins Univ.. USAGianni Pauletta. Universita di Udine. ItalyMarcello Pavan. TR1UMF. CanadaTodd Pedlar. Northwestern Univ.. USAEsa Penttila. Keskeytysvakuutus Yhito Otso. FinlandCharles Perdrisat, College of William & Mary. USARoy Peterson. Univ. of Colorado. USAHelmut Piel. Univ. of Wuppertal. GermanyLeo Piilonen. VPI/State Univ.. USALawrence Pinsky. Univ. of Houston. USADaniel Pitzl. Univ. of California. Santa Cruz. USADinko Pocanic. Univ. of Virginia. USALeonid Ponomarev. N.V. Kurchalov Institute of Atomic

Research. RussiaYouri Popov, Joint Institute for Nuclear Research. Dubna.

RussiaRahman Pourang, College of William & Mary. USADieter Proch. DESY. GermanyYuri Prokoshkin. Institute for High Energy Physics,

RussiaVina Punjabi. Norfolk State Univ.. USASun Qian. Rutgers Univ.. USAXi-Jun Qiu. Shanghai Institute for Nuclear Research, PRCKenneth Quon, Boston Univ.. USAFriedrich Rab?nstein. Univ. of New Mexico. USATomas Radcliffe. California Institute of Technology. USARonald Ransome. Rutgers Univ.. USAMohini Rawool-Sullivan, Los Alamos National

Laboratory. USAR. Ray. Univ. of Texas at Austin. USAHooman Razani. Royal Institute of Technology. UKDavid Read. Univ. of Texas at Austin, USAGlen Rebka, Jr.. Univ. of Wyoming. USAJames Redmon, Abilene Christian Univ.. USAPaul Reeder. Battelle Pacific Northwest Lab.. USARandolph Reeder, Univ. of New Mexico. USALuigi Rezzonico. Paul Scherrer Institute. SwitzerlandSteve Richards. Cryomag Services. Inc.. USAJeffrey Richman. Univ. of California. Santa Barbara, USACarla Riedel-Edwards. Univ. of Minnesota. USAPeter Riley. Univ. of Texas at Austin. USARobert Ristinen. Univ. of Colorado. USABarry Ritchie. Arizona State Univ.. USAN. Roberson. Duke Univ.. USADonald Roberts. Univ. of Michigan, USAJeanette Roberts Los Alamos National Laboratory. USAPhilip Roos. Univ. of Maryland. USAAndrew Rose. Abilene Christian Univ.. USAThomas Roser. Univ. of Michigan. USAGunther Rosner. Univ. of Main/. GermanyMarvin Rou.'ih. Univ. of Maryland. USA

LRMPF Uisitors During 1991

David Rowntree. MIT. USAKaroly Rozsa. Central Research Institute for Physics.

HungarySteven Rugari. George Washington Univ.. USAMichael Sadler. Abilene Christian Univ., USAThomas Sams. Laboraloire National Salurne. FranceLorenzo Santi. Universita degli Studi, ItalyMiguel Sarmiento. Northwestern Univ.. USAPeter Sauer. Univ. of Hannover, GermanyAlexander Saunders. Univ. of Colorado. USADavid Saunders. United Stales Air Force Academy. USAMasuru Sawaki. Hammamutus Corporation. JapanFrank Schaefer. Nonaffiliated, GermanyDonald Schnitzler. Linfield College. USAJos Schouten. Oxford Instruments. USAPaul Schultze. Abilene Christian Univ., USAHardy Seifert. Justus-Liebig-Universitat Giessen.

GermanyRyoichi Seki. California Institute of Technology. USAKiimal Seth, Northwestern Univ., USAAnil Sethi, Univ. of Minnesota. USAPaula Setters. LaRue County High School. USASergei Sharamentov. Institute for Nuclear Research.

RussiaEduard Sharapov. Joint Institute for Nuclear Research.

Dubna, RussiaJeffrey Shaw. Rensselaer Polytechnic Institute. USATokushi Shibata. Univ. of Tokyo, JapanTatsuo Shikama, Tohoku Univ.. JapanToniika/.u Shima. Texas A&M Univ.. USAHirohiko Shiinizu. Kyoto Univ., JapanYuri Shiyan, Soviet Academy of Sciences, RussiaAnthony Shoup. Univ. of California. Irvine. USAPeter Stegel, California State Polytechnic Institute. USANeven Simicevic. MIT. USAAnthony Simon. Texas A&M Univ.. USADarrel Smith, Embry-Riddle Aeronautical Univ.. USADouglas Smith. Univ. of Pennsylvania, USAGregory Smith. TRIUMF. CanadaL. Smith. Univ. of Virginia, USAW. Smythe. Univ. of Colorado, USAMichael Snell. United Slates Air Force Academy/DFP.

USAPaul Souder. Syracuse Univ., USAHarold Spinka. Argonne National Laboratory, USAShirvel Stanislaus. Valparaiso Univ.. USAKeith Stantz. Indiana Univ.. USAGeoffrey Stapleton. Continuous Electron Beam

Accelerator Facility, USAMichael Stark. Univ. of Maryland, USAYuri Stavissky. Academy of Sciences. RussiaChristian Stratton. Univ. of California, Irvine. USAWilliam Strossman. Univ. of California. Riverside. I'SAJames Stubbins. Univ. of Illinois. Urbana. USALarry Suddarth. Univ. of Virginia. USA

flPPENDIH CLHMPF Uisitors During 1991

Evan Sugarbaker, Ohio State Univ.. USAAnthony Sullivan, CERN, SwitzerlandZuxun Sun, Chinese Academy of Sciences, PRCIvan Supek, Los Alamos National Laboratory, USAJeremy Sutton, Oxford Instruments, USAJohn Syzmanski, Indiana Univ., USAPeter Tandy, Kent State Univ., USAChen-Yau Tang, Univ. of New Mexico, USARalph Thomas, Lawrence Livermore National Laboratory,

USAIan Thorson, TR1UMF, CanadaW. Tippens, Univ. of California. Los Angeles, USARobert Tribble, Texas A&M Univ., USAGerald Tripard, Washington State Univ., USATakahiro Tsutsumi, Univ. of New Mexico, USAJavier Urbina, New Mexico State Univ., USALeo Van Ausdeln, Texas A&M Univ., USAAlexandre Varfolomeev, N.V. Kurchatov Institute of

Atomic Energy. RussiaYevgenij Veretenkin, Institute for Nuclear Sciences,

RussiaVladimir Vermul, Institute for Nuclear Research, RussiaWayne Vernon, Univ. of California, San Diego, USASteven Vigdor, Indiana Univ., USAHansdeter Vogel, Interatom, GMBH, GermanyPetr Vogel, California Institute of Technology, USAMassimo Volta, United States Naval Academy, USAJan Vrana, Univ. of Pris-Sud, FranceGerhard Wagner, Physikalisches Instilut, GermanyGeorge Walker, Indiana Univ.. USAMichael Wall, Univ. of Virginia, USAChristian Walter, Paul Scherrer Institute, SwitzerlandJochen Wambach, Univ. of Illinois, Urbana, USAMark Wang, MIT, USAMinghong Wang, New Mexico State Univ., USAHerbert Ward. Univ. of Texas at Austin, USADouglas Watson, Univ. of York, UKMonroe Wechsler, Iowa State Univ., USADaniel Weeks, Univ. of New Mexico, USAJohn Wefel, Louisiana State Univ.. USAHans Weidenmuller. Max-Planck-Inslutiit fiir

Kernphysik, GermanyZeev Weinfeld, Tel-Aviv Univ., IsraelT. Welch, Univ. of Virginia, USAHenry Weller, Duke Univ., USAStewart Wennersten, George Washington Univ., USA

Heinz Weyer, Basel Univ.. SwitzerlandBlane Wheeler. Eastern New Mexico Univ.. US"ACharles Whitley. Univ. of Texas at Austin. USAColin Wilburn, Micron Semiconductor, Inc., USABryan Wildenthal. Univ. of Nev Mexico. USAMarkus Wildi, Physikalisches Institut der Univ. Basel,

SwitzerlandDenys Wilkinson, Nonaffiliated, UKAllen Williams, Univ. of Pennsylvania. USADavid Williams, Univ. of California, Santa Cruz. USAKevin Wilson, MIT, USAVictoria Wischer Univ. of Texas, El Paso, USARandolph Wojick, Continuous Electron Beam Accelerator

Facility, USAHermann Wollnik, Universitat Gieben, GermanyHenry Wong, Paul Scherrer Institute, SwitzerlandHeather Woolverton, Univ. of Central Arkansas, USADavid Works, Temple Univ., USASteven Worm, Univ. of Texas at Austin, USABryan Wright, Univ. of Virginia, USAS. Wright, Univ. of Chicago, USADing Wu, Institute of Applied Physics and Computer

Mathematics, PRCJui-Pin Wu, Univ. of California, Riverside, USAYing Xiao, Temple Univ., USAJianguo Xu, Syracuse Univ., USAKerem Yaman, Univ. of Pennsylvania, USAXue Yao, Univ. of Houston, USAZhiquan Yao, Shanghai Institute of Nuclear Research, PRCJennifer Yeh, Harvard Univ., USATodd Yilk, Yale Univ., USAGaurang Yodh, Univ. of California, Irvine. USAHitashi Yokobori, Japan Atomic Energy Research

Institute, JapanYoichiro Yoshida. Ohbayashi Corporation, JapanRobert Youngblood, Brookhaven National Laboratory,

USAMark Yuly, MIT, USAAnatolij Zclensky, Institute for Nuclear Research. RussiaYi-Ding Zhang, Virginia Polytechnic Institute, USABing Zhou, Boston Univ., USAZongyuan Zhou, Nanjing Univ., PRCKlaus Ziock, Univ. of Virginia, USAGisbert zu Putlitz, Physikalisches Insiitiit der

Uiiiversitat, GermanyJohn Zumbro, Los Alamos National Laboratory. USA

170

Information for Contributors

Information for contributors

Progress at LAMPF is the progress report of MPDivision of Los Alamos National Laboratory. Inaddition, it includes brief reports on research done atLAMPF by researchers from other institutions and LosAlamos National Laboratory divisions.

Progress at LAMPF is published annually onApril 1. This schedule requires that manuscripts bereceived by December 1.

Published material is edited to the standards of theStyle Manual of ihe American Institute of Physics.Papers are not refereed, hence presentation in this reportdoes not constitute professional publication of thematerial nor does it preempt publication in other journals.Readers should recognize that results reported in Progressat LAMPF are sometimes preliminary or tentative andthat authors should therefore be consulted in the event thatthese results are cited.

Contributors can expedite the publication process bygiving special care to the following specifics:

I. When possible, furnish computer files for textand MAPPER files for illustrations, together witha hard copy of your paper. Progress at LAMPFcan accept files from computers, stand-alone wordprocessors, and personal computers. TeX filesare especially welcome.

2. Drawings and figures submitted should be ofquality suitable for direct reproduction afterreduction to single-column width, 55 mm (2-1/4in.). MAPPER files should be printed on laserprinters.

6.

7.

Figure captions and table headings must befurnished. The AIP Style Manual requires thatevery figure have a caption that is "complete andintelligible in itself without reference to thetext."References must be complete and accurate. If areference t:te>. a paper submitted for publication,the title of the paper and the journal where it hasbeen submitted or where it is to be publishedmust be given. Laboratory standards prefer thatsix authors be listed before et al. is used inreference lists.Abbreviations and acronyms should be avoided ifpossible (in figures and tables as well as text),and when used must be defined.All numerical data should be given in SystemeInternational (SI) units.Authors are reminded that it helps the reader tohave an introduction that states the purpose(s) ofthe experiment before presentation of the data.

Research reports should be brief but complete. A list ofrecent publications relating to the experiment, for separatetabulation in this report, is much appreciated.

Contributors are encouraged to include as authors allparticipants in experiments so that they may receive creditfor authorship and participation.

Questions and suggestions should be directed to KarenPoelakker, Los Alamos National Laboratory, MS H846,Los Alamos, NM 87545, telephone number(505) 667-2928 or BITNET:KAREN@LAMPF.

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