K. Slifer, UNH

K. Slifer, UNH

g2p & the LT Spin Polarizability

for the E08-027 Collaboration

E08-027

June 9, 2011

Inclusive ScatteringInclusive Scattering

€

W

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

Inclusive Polarized Cross Section SFs parameterize everything

we don’t know about proton

structure

Proton g1 also well known

Unpolariz

ed SF a

re v

ery w

ell know

n

0.015 < Q2 < 30

Proton World Data Proton World Data

Q2 = 1.3 and 5

g2 not quite as good...g1really well determined

0.015 < Q2 < 30

Proton World Data Proton World Data

Q2 = 1.3 and 5

g2 not quite as good...g1really well determined

E08-027 : Proton g2 Structure Function Fundamental spin observable has never been measured at low or moderate Q2

BC Sum Rule : violation suggested for proton at large Q2, but found satisfied for the neutron & 3He.

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

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.

BC

Su

m R

ule

Camsonne, Crabb, Chen, Slifer(contact)

g2 data strongly anticipated by theorists

Sp

in P

ola

riza

bili

ty

LT

Experimental Technique Inclusive Polarized Cross Section differences

We Need:

Polarized proton target (Principals: C. Keith, D. Crabb)upstream chicane (Project Lead: T. Michalski)downstream local dump (Design: 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

•Goal is to measure g2p in the low Q2 region with a precision ~ 5-7% by measuring transversely polarized cross section difference = A x Measure both asymmetries and cross sections to 4-5%

•In addition to statistics, we need to control total systematics to 3-5%, i. e., each system to be below that (1-3%).

•Main systematics for asymmetries: • Target polarization (3-4%)• Beam polarization (2-3%)• Dilution factor/packing factor (some cancellation)

•Main systematics for cross sections• Acceptance/optics (~3%) • Dilution factor/packing factor (some cancellation)• Density (2-3%) • Beam charge (1-2%)• Position and angle determination (0.1-0.2 mm, 0.03-0.05 degree)• Detector efficiencies (~< 1%)• Background (pions, …) (1%)• Radiative corrections (including radiative tails) (1-4%)• …

Experimental Goal/Considerations

slide courtesy of JP Chen

Readiness Review May 6, 2011

http://hallaweb.jlab.org/experiment/g2p/review/

Full Report available at:

Physics Manpower

Faculty and Staff (near fulltime effort)

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

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

Don Crabb (UVA) : Target Expert.

Karl Slifer : Contact Person onsite fulltime summer, fall, and ½ of spring.

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

Pengjia ZhuUSTC

Min HuangDuke

Melissa CummingsW & M

Ryan ZielinskiUNH

Toby BadmanUNH

Chao GuUVa

E08-027 Grad Students

+ Temple student?

Jixie ZhangJLab

Geant 4, Optics

James MaxwellUNH

Target, Spin Structure

Kalyan AlladaJLab

Beamline, 3rd Arm

E08-027 Post-Docs

+ Post-Docs (Part-time effort)

Hovhannes Baghdasaryan (UVa)

Narbe Kalantarians(UVa)

Sarah Phillips (UNH)

Xiaohui Zhan (Argonne)

People Power and Tasks

• Overall coordination:Project manager (Jian-ping Chen, Hall A)

Project coordinator for beamline (Tim Michalski, engineering division) Collaboration contacts: Karl Slifer (g2p), Guy Ron (GEp)•Beamline Engineering Division/Accelerator Division (Tim Michalski coordinator)

Engineer/design (Butch Dillon-Townes)Installation (Neil Wilson)

Instrumentation/magnets/vacuum/alignment/software/radcon groups, as identified in 6-month-down schedule/planning

Users (Alexandre Camsonne and Pengjia Zhu) on BCM/BPM/Slow raster…• Target

Target Group (Chirs Keith) UVA(Don Crabb, Donal Day, psotdocs and students)

New Hampshire (Karl Slifer, James Maxwell)Other postdocs/students

• Hall A engineering/design: Septa/LC Dump/Pivot Layout … Hall A engineering/design team (Robin Wines, Al, Gavalya)

With input from the collaboration• Hall A installation

Hall A installation team (Ed Folts)•Simulation/optics/HRS/detectors/DAQ/3rd Arm Users(Physicists/postdocs/students)


• Main Items, each has it’s schedule and milestones (separate talks) Beamline Target Hall infrastructure, beam dump, septa Installation • May, 2011, Main design complete. • End of May, 2011 Target magnet cool-down in EEL• July, 2011, Parts manufactured and arrived• Aug 3, 2011, Beamline region 1 installation complete• Aug 16, 2011, Beamline region 2 installation complete• Mid-late Aug, 2011, Target test in EEL• Sept 1, 2011, Septa, LC beam dump, scattering chamber installed.• Sept 1, 2011, Target move to Hall A for installation• Sept 15, 2011, Beamline region 3 installation complete• Oct 1, 2011, Dump/target/magnet/chamber alignment complete• Oct 10, 2011, Beamline alignment complete• Nov 14, 2011, Target cool-down/polarize • Nov 19, 2011, Experiment Commission Starts• Jan 23 – March16, 2012, Remove Septa, Move Target back to Pivot• May 2012, End of experiment data taking

Schedule and Milestones


• FY11 addition funding from DOE has been confirmed on the way.

• User groups contribution to procurement/machining : UVa (Don/Donal): target magnet repair, material irradiation Temple (Zein-Eddine): procurement Rutgers (Ron): machining + procurement UVa (Nilanga): machining HUJI (Guy): machining + procurement UNH (Karl): procurement Nice to have these contributions

Budget and User Contributions


slide courtesy of C. Keith

Target Status (C. Keith and Target group)

1st test: Mid May Located and repaired leak in the indium seal during initial LN2 cooldown.

2nd test: Late MayPerformed successful (but limited) cooldown of Magnet May 30

cooled magnet to liquid Helium temperature

ramped to full field (5T) and held in persistent mode for 20 mins and ramped down

No Quench

Next day did not have enough Helium to continue. Loss rate greater than expected.

Bottom Line : Magnet seems healthy, some concern over leaks.

Target group wants to thoroughly leak-test before next full cooldown.

Plan to do another full cooldown when leaks are better understood.

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.





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





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’ve addressed this by:

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

b) Manipulating incident angle of the electron beam.

Bottom Line

All the physics proposal goals are still attainable.

JLab support in dealing with this issue has been phenomenal !

Beamline/Accelerator/Design/Installation/Target

reach Q2 = 0.03 GeV2

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

Manipulate the incident beam angle

but 2.5T => PT = 40%

Solution

reach Q2 = 0.03 GeV2

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

Manipulate the incident beam angle

but 2.5T => PT = 40%

can regain some statby changing from 0.5 cm

target to 3 cm.

Large W kinematicsare typically the

most time consumingso they’ve been

trimmed.

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

Rates / Schedule

Runplan

SEPTA IN

SEPTA OUT

Runplan

run at ½ fieldand nonzero incident

angle for lowest energies

Runplan

Beam Allocation is 87 days + 21 commissioning,

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

Draft Schedule

Summary

Recently passed JLab Readiness reviewSome issues to address, but mostly positive evaluation

Target Magnet is onsite and appears to be in good shapeAnother full cooldown will be done prob in next few weeks.

RunPlan and kinematic configuration request has been submitted to the scheduling committee1.1 GeV and 1.7 GeV will have to be negotiated with other halls

Installation is under way in the hallLots of work to finish before the FallCollaborators welcome!

Documents

K. Slifer, UNH