K. Slifer, UNH g2p & the LT Spin Polarizability for the E Collaboration E June 9, 2011

Inclusive Scattering ° * When we add spin degrees of freedom to the target and beam, 2 Additonal SF needed. Inclusive Polarized Cross Section SFs parameterize everything we don’t know about proton structure

Proton g 1 also well known Unpolarized SF are very well known

0.015 < Q 2 < 30 Proton World Data Q 2 = 1.3 and 5 g2g2 not quite as good... g1g1 really well determined

0.015 < Q 2 < 30 Proton World Data Q 2 = 1.3 and 5 g2g2 not quite as good... g1g1 really well determined

E : Proton g 2 Structure Function Fundamental spin observable has never been measured at low or moderate Q 2 BC Sum Rule : violation suggested for proton at large Q 2, but found satisfied for the neutron & 3 He. Spin Polarizability : Major failure (>8  of  PT for neutron  LT. Need g 2 isospin separation to solve. 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. BC Sum Rule Camsonne, Crabb, Chen, Slifer(contact) g 2 data strongly anticipated by theorists Spin Polarizability  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 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

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 ( mm, 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, 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 E manpower Guy Ron, Doug Higinbotham, Ron Gilman, Donal Day, John Arrington, Adam Sarty......

Pengjia Zhu USTC Min Huang Duke Melissa Cummings W & M Ryan Zielinski UNH Toby Badman UNH Chao Gu UVa E Grad Students + Temple student?

Jixie Zhang JLab Geant 4, Optics James Maxwell UNH Target, Spin Structure Kalyan Allada JLab Beamline, 3 rd Arm E 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/3 rd Arm Users(Physicists/postdocs/students) slide courtesy of JP Chen

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 slide courtesy of JP Chen

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 JP Chen

slide courtesy of C. Keith

Target Status (C. Keith and Target group) 1 st test: Mid May Located and repaired leak in the indium seal during initial LN2 cooldown. 2 nd test: Late May Performed 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: 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’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 Q 2 = 0.03 GeV 2 run the two lowest energies with only 2.5 T target field & Manipulate the incident beam angle but 2.5T => P T = 40% Solution

reach Q 2 = 0.03 GeV 2 run the two lowest energies with only 2.5 T target field & Manipulate the incident beam angle but 2.5T => P T = 40% can regain some stat by changing from 0.5 cm target to 3 cm. Large W kinematics are typically the most time consuming so 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 field and 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 review Some issues to address, but mostly positive evaluation Target Magnet is onsite and appears to be in good shape Another full cooldown will be done prob in next few weeks. RunPlan and kinematic configuration request has been submitted to the scheduling committee 1.1 GeV and 1.7 GeV will have to be negotiated with other halls Installation is under way in the hall Lots of work to finish before the Fall Collaborators welcome!