overview bremsstrahlung tagging spectrometer and photon beam review
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1Elton S. Smith University of Virginia October 25, 2005
OverviewBremsstrahlung Tagging Spectrometer
and Photon Beam Review
Elton S. Smith
Jefferson Lab
RequirementsSummary of beamline and ratesStatus of project
2Elton S. Smith University of Virginia Oct 25, 2005
Normal mesons:glue is passive
Hybrid mesons:glue is excited
q q
The physics goal of GlueX is to map the spectrum of hybrid mesons starting with those with the unique signature of exotic JPC .
Identifying JPC requires an amplitude analysis which in turn requires• linearly polarized photons• detector with excellent acceptance and resolution• sensitivity to a wide variety of decay modes which include photon and charged particles
This, coupled with a hybrid mass reach up to 2.5 GeV, requires 9 GeV photons produced using coherent bremsstrahlung from 12 GeV electrons.
Physics goals and key features
3Elton S. Smith University of Virginia Oct 25, 2005
The GlueX Detector Design has been driven by the need to carry out Amplitude analysis.
p
X
n,p
Photoproduction
1 → a+1 → ()() →
h0 → bo1→ () →
Final state particles ± K± p n KL
h’2 → K+1K− → o K+ K− → +−K+K−
1 1 ’1 b2 h2 h’2 b0 h0 h’0
all charged
many photons
strange particles
1−+ 2+− 0+−
Search for QCD Exotics
4Elton S. Smith University of Virginia Oct 25, 2005
Mass Predictions
Lowest mass expected to be 1(1−+) at 1.9±0.2 GeV
Lattice 1-+ 1.9 GeV2+- 2.1 GeV0+- 2.3 GeV
5Elton S. Smith University of Virginia Oct 25, 2005
Line shape distortion
M=2.5 GeV M=2.8 GeV
MX (GeV)
6Elton S. Smith University of Virginia Oct 25, 2005
p p
M
J=0– or 0+
V
X
photon
for X, J = 0
Center of Mass of V
X = exchange particle
L 0, 1, or 2
PV P PX 1 L
V = vectorphoton
m = 1
m = -1
R
L
AN AU
Parity conservation implies:
are sensitive to production mechanism
V = vectorphoton
m = 1
m = -1L AN AU
7Elton S. Smith University of Virginia Oct 25, 2005
Strategy for Exotic Meson Discovery Use 8 – 9 GeV polarized photons (12 GeV electron beam)
─ Sensitivity to mesons masses up to 2.5 GeV
─ Expect production of hybrids to be comparable to normal mesons
─ Dearth of experimental data
Use hermetic detector with large acceptance
─ Decay modes expected to have multiple particles
─ hermetic coverage for charged and neutral particles
─ high data acquisition rate to enable amplitude analysis
Perform partial-wave analysis
─ identify quantum numbers as a function of mass
─ check consistency of results in different decay modes
8Elton S. Smith University of Virginia Oct 25, 2005
Requirements for photon beam
Coherent peak ~ 8.4 ─ 9 GeV
Linear polarization
High rates
─ Initial running at 107 /s in the coherent peak
─ Design system with a clear path to 108 /s
9Elton S. Smith University of Virginia Oct 25, 2005
6 GeV CEBAF
CHL-2CHL-2
Upgrade magnets Upgrade magnets and power and power suppliessupplies
12
Enhance equipment in Enhance equipment in existing hallsexisting halls
add Hall D (and beam line)
10Elton S. Smith University of Virginia Oct 25, 2005
Hall D Complex
Accelerator East Arc
11Elton S. Smith University of Virginia Oct 25, 2005
Top View
75 m
Tagger Area
ExperimentalHall D
Electron beam
Coherent Bremsstrahlungphoton beam
Solenoid-Based detectorCollimator
PhotonBeam dump
East arc
North linac
Tagger area
Hall D
ElectronBeam dump
Photon beam and experimental area
12Elton S. Smith University of Virginia Oct 25, 2005
GlueX / Hall D Detector
Electron Beam from CEBAF
Lead GlassDetector
Solenoid
Coherent BremsstrahlungPhoton Beam
Tracking
TargetCerenkovCounter
Time ofFlight
BarrelCalorimeter
Note that tagger is80 m upstream of
detector
Detector ReviewOct 20-22, 2004
13Elton S. Smith University of Virginia Oct 25, 2005
GlueX detectorCapability Quantity Range
Charged particles Coverage 1o < < 170o
Momentum Resolution (5o-140o) p/p = 1 − 2%
Position resolution = 150-200 m
dE/dx measurements 20 < < 140o
Time-of-flight measurements t = 60 ps
Cerenkov and /K separation < 14o
Barrel time resolution t < (150 + 50 /√E) ps
Photon detection Energy measurements 2 < < 120o
Veto capability > 120o
Barrel energy resolution (E > 20 MeV) E/E = (2 + 5/√E)%
Lead glass energy resolution (E > 100 MeV) E/E = (3.6 + 7.3/√E)%
Barrel position resolution z ~ 4 cm
Lead glass position resolution x,y = 0.7 cm
DAQ/trigger Level 1 200 kHz at 108/s
Level 3 event rate to tape 15 kHz
Data rate 100 MB/s
Electronics Fully pipeline Flash ADCs, multi-hit TDCs
Photon Flux Tagged rate Initially: 107 /s, Final: up to 108 /s
14Elton S. Smith University of Virginia Oct 25, 2005
The GlueX collaboration has designed and optimized the detector to study gluonic excitations. Many university groups have contributed to the R&D and development of major subsystems.
• Solenoid JLab
• Detectors• Tracking Carnegie Mellon, Ohio U, Florida International U
• Calorimetry U of Regina, Florida State, Indiana U, Inst for High Energy Physics (Protvino), U of Athens
• PID Indiana U, Inst for High Energy Physics, U of Tenn, ORNL
• Computing JLab, U of Regina, Indiana U, Carnegie Mellon, U Connecticut, Christopher Newport U
• Electronics Indiana U, JLab, U of Alberta, Indiana U Cyclotron
• Beamline Catholic U of America, Glasgow U, U of Connecticut
• Infrastructure JLab
Institutional Responsibilities
15Elton S. Smith University of Virginia Oct 25, 2005
Interface between accelerator and Hall D
The accelerator will be responsible for the electron beamline, and Hall D will be responsible for the photon beam. This is the nominal breakdown of responsibilities, with additional clarification in the next two paragraphs.
The accelerator will deliver and monitor the 12 GeV electron beam to the radiator immediately upstream of the tagger magnet. The accelerator will also be responsible for steering the beam to the electron beam dump. Some monitoring of the electron beam at the dump may be required to insure accurate delivery.
Hall D will be responsible for purchasing and qualifying the crystal radiators, all aspects of the tagger magnet and hodoscope systems, collimation of the photon beam immediately upstream of the photon hall, and monitoring of the photon beam from the radiator to the photon beam dump behind the GlueX detector.
16Elton S. Smith University of Virginia Oct 25, 2005
flu
x
photon energy (GeV)
12 GeV electrons
This technique provides requisite energy, flux
and polarization
collimated
Incoherent &coherent spectrum
tagged
0.1% resolution
40%polarization
in peak
electrons in
photons out
spectrometer
diamondcrystal
Coherent Bremsstrahlung
Hadronic Backgrounds
17Elton S. Smith University of Virginia Oct 25, 2005
High sensitivity → high rates
Start with
8.4 - 9.0 GeV Tagged
107 / s
current 300 nA
radiator 10 4
No 2 108 / s
30 cm targetcross section = 120 µb
R taggedhadronic 1.4 kHz R total
hadronic 37 kHzlow-rate
high-rates: multiply by factor of 10
18Elton S. Smith University of Virginia Oct 25, 2005
peak energy 8 GeV 9 GeV 10 GeV 11 GeV
N in peak 185 M/s 100 M/s 45 M/s 15 M/s
peak polarization 0.54 0.41 0.27 0.11 (f.w.h.m.) (1140 MeV) (900 MeV) (600 MeV) (240 MeV)
peak tagging eff. 0.55 0.50 0.45 0.29 (f.w.h.m.) (720 MeV) (600 MeV) (420 MeV) (300 MeV)
total hadronic rate 385 K/s 365 K/s 350 K/s 345 K/s(in tagged peak) (26 K/s) (14 K/s) (6.3 K/s) (2.1 K/s)
1. Total hadronic rate is dominated by the resonance region
2. For a given electron beam and collimator, background is almostindependent of coherent peak energy, comes mostly from incoherent part.
3. The following assumes a 12GeV electron beam energy.
Photon Beam Rates and Backgrounds
19Elton S. Smith University of Virginia Oct 25, 2005
Today’s presentations
Photon beam
Electron beam
4. Tagger magnet design5. Spectrometer optics
Vacuum chamber
75 m
Electron beamDetectorCollimator
PhotonBeam dump
Hodoscope:6. Fixed array and beam monitoring7. Tagger Microscope
1. Overview2. Photon beam3. Simulation and backgrounds
20Elton S. Smith University of Virginia Oct 25, 2005
Architect’s rendering of Hall D complex
Service Buildings
Hall D
Cryo Plant
Counting House
22Elton S. Smith University of Virginia Oct 25, 2005
JLab 12 GeV Upgrade Project Status
Successful Project Review (Jul 2005), CD-1 expected soon
Four-year construction project planned to start in FY08
Review of Science program for the 12-GeV Upgrade (Apr 2005)From the Executive Summary: “After a decade of research, we should know whether the formation of flux tubes by the gluon fields is the mechanism of confinement…”
Highlight in the 20-year plan of the Office of Science (2003)
What’s New: “New supercomputing studies indicate that force fields called “flux-tubes” may be responsible [for the mechanism that confines quarks], and that exciting these should lead to the creation of never-before-seen particles.”
Determination of “Mission Need” CD-0 (Apr 2004)
23Elton S. Smith University of Virginia Oct 25, 2005
GlueX Reviews
December 1999: PAC Requested Review of the GlueX ProjectD. Cassel (chair), J. Domingo, W. Dunwoodie, D. Hitlin, G. Young.
April 2001: NSAC Long Range Plan Committee.
July 2003: Electronics Review of the GlueX ProjectJ. Domingo, A. Lankford, G. Young (chair)
October 2004: Detector ReviewM. Albrow, J. Alexander (Chair), W. Dunwoodie, B. Mecking.
December 2004: Solenoid AssessmentJ. Alcorn, B. Kephart (Chair), C. Rode.
All of these review committees have both identified areas that were unsettled and made excellent suggestions for improvements
24Elton S. Smith University of Virginia Oct 25, 2005
Hall D Organizational Chart
Proposal for mergingGlueX collaboration with12-GeV Upgrade ProjectOrganization reflectsthe WBS outline
25Elton S. Smith University of Virginia Oct 25, 2005
Summary Mapping the spectrum of hybrid mesons provides essential
experimental data on the physics of the strong interactions at low energies in the region of confinement.
This unique experimental program is possible now due to
─ increases in computational power
─ new developments in detector readout technology
─ to high quality electron beam at the 12-GeV CEBAF Upgrade
─ technology to produce thin diamond crystals
You are asked today to review the conceptual design of the Hall D tagger spectrometer and the design parameters of the photon beam for use in this experimental program.
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