K. Slifer, UNH

JLab Readiness Review

for the E08-027 Collaboration

E08-027

May 6, 2011

Inclusive ScatteringInclusive Scattering

€

W

° * Q2 : 4-momentum transferX : Bjorken Scaling varW : Invariant mass of target

Kinematics1st order Feynman diagram

Inclusive ScatteringInclusive Scattering

€

W

° *

Inclusive Cross Section deviation from point-like behavior

characterized by the Structure Functions

1st order Feynman diagram

Q2 : 4-momentum transferX : Bjorken Scaling varW : Invariant mass of target

Inclusive ScatteringInclusive Scattering

€

W

° * When we add spin degreesof freedom to the targetand beam, 2 Addiitonal SFneeded.

Inclusive Polarized Cross Section SFs parameterize everything

we don’t know about proton

structure

E08-027 : Proton g2 Structure Function

Primary Motivation

Proton g2 structure function has never been measured at low or moderate Q2.

We will determine this fundamental quantity at the lowest

possible Q2

This will help to clarify several outstanding puzzles

Hydrogen HyperFine Splitting : Lack of knowledge of g2 at low Q2 is one of the leading uncertainties.

Proton Charge Radius : also one of the leading uncertainties in extraction of <Rp> from H Lamb shift.

A. Camsonne J.P. Chen D. Crabb K. Slifer

Structure dependent effects in Q.E.D.Hydrogen Hyperfine StructureProton Charge Radius

Systematic uncertainty In Measurements of

Measure of QCD complexity

Ideal place to test ÂPT calcs

Spin Polarizability

SUM RulesExtended GDH SUMBC SUm RuleELT SUM Rule

Burkhardt Cottingham Sum Rule

predicted to vanish for all Q2

= 0

BC Sum RuleBC Sum Rule

P

N

3He BC satisfied w/in errors for 3He

BC satisfied w/in errors for Neutron

(But just barely in vicinity of Q2=1!)

0<x<1

BC Sum RuleBC Sum Rule

P

N

3He

BC satisfied w/in errors for JLab Proton2.8 violation seen in SLAC data

0<x<1

BC Sum RuleBC Sum Rule

P

N

3He

BC satisfied w/in errors for JLab Proton2.8 violation seen in SLAC data

0<x<1

Mostly unmeasured

Spin Polarizabilities

Major failure (>8 of PT for neutron LT.

this is the region we should start to be able to trust PT

similar problem for proton 0

Finite Size Effects

Hydrogen HyperFine Splitting : Lack of knowledge of g2 at low Q2 is one of the leading uncertainties.

Proton Charge Radius : also one of the leading uncertainties in extraction of <Rp> from H Lamb shift.

nucleus ≈ 10-15

Atom ≈ 10-10

The finite size of the nucleon (QCD) plays a small but significant role in calculating atomic energy levels in QED.

Proton Charge Radius from P lamb shift disagrees with eP scattering result by about 6%

<Rp> = 0.84184 ± 0.00067 fm Lamb shift in muonic hydrogen

<Rp> = 0.897 ± 0.018 fm World analysis of eP scattering

<Rp> = 0.8768 ± 0.0069 fm CODATA world average

R. Pohl et.al Nature, July 2010

I. Sick PLB, 2003

Polarizability : Integrals of g1 and g2 weighted by 1/Q4

Zemach radius : Integral of GEGM weighted by 1/Q2

Dominated by Kinematic region of E08-027 and E08-007

Experimental TechniqueExperimental Technique

− P

P

Experimental TechniqueExperimental Technique

− − P

P

P

P

Experimental Technique Inclusive Polarized Cross Section differences

We Need:

Polarized proton target (see talks of C. Keith, D. Crabb)upstream chicane (T. Michalski)downstream local dump (A. Gavalya)

Low current polarized beamUpgrades to existing Beam Diagnostics to work at 85 nA (T. Michalski)

Lowest possible Q2 in the resonance regionSepta Magnets to detect forward scattering (A. Gavalya, E. Folts)

Polarized Ammonia Target

5 Tesla Transverse FieldCurrent = 85 nA

Moller Polarimeter

Third arm luminosity monitor for cross-check(not shown).

Compton will not be used.

New Beam Diagnostics for low current

Slow raster for target

Up Stream Chicane

2 Dipoles to compensate for target fieldMagnets on loan from Hall C

Low Power Local Dump

Mag field of target -> beam will not make it to hall dump

Room Temperature Septum Magnets

-Used in Prex, modified with new coils.-bend 5.6o to 12.5o

-allow access to lowest possible Q2

Source (%)

Cross Section 5-7

PbPT 4-5

Radiative Corrections 3

Parallel Contribution <1

Total 7-9

Systematic Error Budget

Statistical error to be equal or better at all kins

BC Sum Rule Spin Polarizability LT

Projected Results

Proposal Kinematics

EG4: g1p E08-027 : g2p

0.02 < Q2 < 0.5 GeV2

Resonance Region

Changes from Proposal

Room temp septa magnets instead of cryo septa for co-existence with QWeak.

leads to a small gap in coverage at large Q2, but the min Q2 is unchanged.

requires transition time to remove the septa.

Changes from Proposal

Room temp septa magnets instead of cryo septa for co-existence with QWeak.

leads to a small gap in coverage at large Q2, but the min Q2 is unchanged.

requires transition time to remove the septa.

Target field distorts the scattering plane much more than initial estimates.

If ignored this would push the Q2 coverage to 0.08 GeV2 instead of 0.02 GeV2

Changes from Proposal

Room temp septa magnets instead of cryo septa for co-existence with QWeak.

leads to a small gap in coverage at large Q2, but the min Q2 is unchanged.

requires transition time to remove the septa.

Target field distorts the scattering plane much more than initial estimates.

If ignored this would push the Q2 coverage to 0.08 GeV2 instead of 0.02 GeV2

We can address this by:

a) Running at 2.5 T for the lowest incident energies.

b) Manipulating incident angle of electron beam.

c) Moving the target out of the nominal scattering plane. Best combination

of these sti

ll being

evaluated

Bottom Line

All the physics proposal goals appear to still be attainable. Net result is a shift of lowest Q2 from 0.02 to 0.03 GeV2

We Plan to finalize run configuration within next few days.

None of the configurations under consideration require any new design/construction.

Bottom Line

All the physics proposal goals appear to still be attainable. Net result is a shift of lowest Q2 from 0.02 to 0.03 GeV2

We plan to finalize run configuration within next few days.

None of the configurations under consideration require any new design/construction.

JLab support in dealing with this issue has been phenomenal !

Beamline/Accelerator/Design/Installation/Target

run the two lowest energies with only 2.5 T target field&

Elevate the target 9 cm above nominal scattering plane.

run the two lowest energies with only 2.5 T target field&

Elevate the target 9 cm above nominal scattering plane.

reach Q2 = 0.03 GeV2

run the two lowest energies with only 2.5 T target field&

Elevate the target 9 cm above nominal scattering plane.

but 2.5T => PT = 40%

run the two lowest energies with only 2.5 T target field&

Elevate the target 9 cm above nominal scattering plane.

but 2.5T => PT = 40%

can regain some statby changing from 0.5 cm

target to 3 cm.

still will need to cutsome settings

reach Q2 = 0.03 GeV2

Rates / Schedule

Large W kinematicsare typically the

most time consumingso they’ve been

trimmed.

Optimizing Runplan in Progress

This is the most recent “Least-painful” choice of settings

Draft Schedule

g2p Runplan

SEPTA IN

SEPTA OUT

g2p Runplan

1.7 GeV incompatible with

Qweak

g2p Runplan

Beam Allocation is 87 days + 21 commissioning, so we still have some cutting to do.

g2p Runplan

Beam Allocation is 87 days + 21 commissioning, so we still have some cutting to do.

We expect to find some saving in optimizing the overhead between g2p and GEp

Increasing DAQ rate from 4-8 kHz can save us about 7 calendar days.

Thank you to the committee

Backups

Physics ManpowerPost-Docs (Full-time effort)

Kalyan Allada (Hall A) : Beamline, 3rd arm Luminosity monitor.

James Maxwell (UNH) : Target Expert, SANE veteran, Spin-Physics.

Jixie Zhang (Hall A) : Geant4 simulations, Optics.

Post-Docs (Part-time effort)

Hovhannes Baghdasaryan (UVa)

Narbe Kalantarians(UVa)

Sarah Phillips (UNH)

Xiaohui Zhan (Argonne)

This is a Partial list: More details in JP and Ron’s talks

Physics ManpowerGraduate Students

Tobias Badman (UNH, Slifer): 2nd year, onsite starting June 1.

Melissa Cummings (W&M, Todd Averett), 2nd year, onsite from May 1.

Chao Gu (UVa, Nilanga Liyanaga), 2nd year, onsite.

Min Huang (Duke, Haiyan Gao), 3rd year, onsite, (simulation, optics).

Pengjia Zhu (USTC, Yunxiu Ye), 3rd year, onsite, (beamline, target).

Ryan Zielinski (UNH, Slifer) : onsite starting June 1.

Further expected

A student from Temple (Zein-Eddine Meziani), 2nd year, onsite from May 1?

E08-007 expects 2 further students (Rutgers and HUJI).

This is a Partial list: More details in JP and Ron’s talks

Physics Manpower

Faculty and Staff

Jian-Ping Chen (JLab) : Project manager, overall coordination.

Alexandre Camsonne (JLab): Beam line, DAQ, …

Don Crabb (UVA) : Target Expert.

Karl Slifer : onsite fulltime summer and fall. onsite fullttime every other week in spring.

*For these slides, I’m not counting E08-007 manpowerGuy Ron, Doug Higinbotham, Ron Gilman, Donal Day, John Arrington, Adam Sarty......

This is a Partial list: More details in JP and Ron’s talks

Contribution to Hyperfine Splitting

The 5T magnet field distorts the scattering plane much morethan initial simulations revealed, especially at low momentum

Out of plane scattering angle

Effect discovered by Jixie Zhang (Geant4).confirmed by Min Huang (Snake), John Lerose

If ignored, this would push all the low momentum data to higher Q2

Out of plane scattering angle correction

Spin Polarizabilities

Major failure (>8 of PT for neutron LT. Need g2 isospin separation to solve.

this is the region we should start to be able to trust PT

Even in this scenario, westill reach Q2=0.04 GeV2

“Worst-Case Scenario”

Run lowest energies with 2.5 T field,

Target located in nominal scattering plane.

Incident beam horizontal as it passes thru target.

Overhead Assumptions

~22 days