K. Slifer, UNH JLab Readiness Review for the E Collaboration E May 6, 2011

Inclusive Scattering ° * Q 2 : 4-momentum transfer X : Bjorken Scaling var W : Invariant mass of target Kinematics 1 st order Feynman diagram

Inclusive Scattering ° * Inclusive Cross Section deviation from point-like behavior characterized by the Structure Functions 1 st order Feynman diagram Q 2 : 4-momentum transfer X : Bjorken Scaling var W : Invariant mass of target

Inclusive Scattering ° * When we add spin degrees of freedom to the target and beam, 2 Addiitonal SF needed. Inclusive Polarized Cross Section SFs parameterize everything we dont know about proton structure

E : Proton g2 Structure Function Primary Motivation Proton g 2 structure function has never been measured at low or moderate Q 2. We will determine this fundamental quantity at the lowest possible Q 2 This will help to clarify several outstanding puzzles Hydrogen HyperFine Splitting : Lack of knowledge of g 2 at low Q 2 is one of the leading uncertainties. Proton Charge Radius : also one of the leading uncertainties in extraction of from H Lamb shift. A. Camsonne J.P. Chen D. Crabb K. Slifer

Structure dependent effects in Q.E.D. Hydrogen Hyperfine Structure Proton Charge Radius Systematic uncertainty In Measurements of Measure of QCD complexity Ideal place to test ÂPT calcs Spin Polarizability SUM Rules Extended GDH SUM BC SUm Rule ELT SUM Rule

Burkhardt Cottingham Sum Rule predicted to vanish for all Q 2 = 0

BC Sum Rule P N 3 He BC satisfied w/in errors for 3 He BC satisfied w/in errors for Neutron (But just barely in vicinity of Q 2 =1!) 0<x<1

BC Sum Rule P N 3 He BC satisfied w/in errors for JLab Proton 2.8 violation seen in SLAC data 0<x<1

BC Sum Rule P N 3 He BC satisfied w/in errors for JLab Proton 2.8 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 g 2 at low Q 2 is one of the leading uncertainties. Proton Charge Radius : also one of the leading uncertainties in extraction of from H Lamb shift. nucleus Atom 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% = ± fm Lamb shift in muonic hydrogen = ± fm World analysis of eP scattering = ± fm CODATA world average R. Pohl et.al Nature, July 2010 I. Sick PLB, 2003

Polarizability : Integrals of g 1 and g 2 weighted by 1/Q 4 Zemach radius : Integral of G E G M weighted by 1/Q 2 Dominated by Kinematic region of E and E08-007

Experimental Technique P P

Experimental 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 beam Upgrades to existing Beam Diagnostics to work at 85 nA (T. Michalski) Lowest possible Q 2 in the resonance region Septa Magnets to detect forward scattering (A. Gavalya, E. Folts)

Polarized Ammonia Target 5 Tesla Transverse Field Current = 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 field Magnets 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 5.6 o to 12.5 o -allow access to lowest possible Q 2

Source(%) Cross Section5-7 PbPTPbPT 4-5 Radiative Corrections3 Parallel Contribution<1 Total7-9 Systematic Error Budget Statistical error to be equal or better at all kins

BC Sum Rule Spin Polarizability LT Projected Results

Proposal Kinematics EG4: g1pE : g2p 0.02 < Q 2 < 0.5 GeV 2 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 Q 2, but the min Q 2 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 Q 2, but the min Q 2 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 Q 2 coverage to 0.08 GeV 2 instead of 0.02 GeV 2

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 Q 2, but the min Q 2 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 Q 2 coverage to 0.08 GeV 2 instead of 0.02 GeV 2 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 still being evaluated

Bottom Line All the physics proposal goals appear to still be attainable. Net result is a shift of lowest Q 2 from 0.02 to 0.03 GeV 2 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 Q 2 from 0.02 to 0.03 GeV 2 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 Q 2 = 0.03 GeV 2 run the two lowest energies with only 2.5 T target field & Elevate the target 9 cm above nominal scattering plane. but 2.5T => P T = 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 => P T = 40% can regain some stat by changing from 0.5 cm target to 3 cm. still will need to cut some settings reach Q 2 = 0.03 GeV 2

Rates / Schedule

Large W kinematics are typically the most time consuming so theyve 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 Manpower Post-Docs (Full-time effort) Kalyan Allada (Hall A) : Beamline, 3 rd 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 Rons talks

Physics Manpower Graduate Students Tobias Badman (UNH, Slifer): 2 nd year, onsite starting June 1. Melissa Cummings (W&M, Todd Averett), 2 nd year, onsite from May 1. Chao Gu (UVa, Nilanga Liyanaga), 2 nd year, onsite. Min Huang (Duke, Haiyan Gao), 3 rd year, onsite, (simulation, optics). Pengjia Zhu (USTC, Yunxiu Ye), 3 rd year, onsite, (beamline, target). Ryan Zielinski (UNH, Slifer) : onsite starting June 1. Further expected A student from Temple (Zein-Eddine Meziani), 2 nd year, onsite from May 1? E expects 2 further students (Rutgers and HUJI). This is a Partial list: More details in JP and Rons 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, Im not counting E manpower Guy Ron, Doug Higinbotham, Ron Gilman, Donal Day, John Arrington, Adam Sarty This is a Partial list: More details in JP and Rons talks

Contribution to Hyperfine Splitting

The 5T magnet field distorts the scattering plane much more than 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 Q 2 Out of plane scattering angle correction

Spin Polarizabilities Major failure (>8 of PT for neutron LT. Need g 2 isospin separation to solve. this is the region we should start to be able to trust PT

Even in this scenario, we still reach Q 2 =0.04 GeV 2 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