1. Proton Recoil Polarization in the 4 He(e,e’p) 3 H, 2 H(e,e’p)n, and 1 H(e,e’p) Reactions SHMS Commissioning Session, Hall C Workshop. August 20, 2011. Spokespersons: E.J. Brash, G.M. Huber, R. Ransome, S. Strauch

2. Dr. Garth Huber, Dept. of Physics, Univ. of Regina, Regina, SK S4S0A2, Canada. 2 Scientific Objectives Investigate the role of nuclear medium modifications via proton recoil polarization in quasielastic (e,e’p) Investigate the role of nuclear medium modifications via proton recoil polarization in quasielastic (e,e’p) High sensitivity to nucleon structure while at same time least sensitive to conventional nuclear medium effects. High sensitivity to nucleon structure while at same time least sensitive to conventional nuclear medium effects. Key features Impact Wide coverage of proton virtualities at Q 2 =1.0 GeV 2 Study the momentum (virtuality) dependence of nucleon medium effects 4 He, 2 H, 1 H targets Study the density dependence of nucleon medium effects High-precision data point of the proton recoil polarization in 4 He(e,e’p) 3 H at Q 2 =1.8 GeV 2 Compare free and bound proton recoil polarizations where models predict largest sensitivity to effect of in-medium form factors

3. Dr. Garth Huber, Dept. of Physics, Univ. of Regina, Regina, SK S4S0A2, Canada. 3 Kinematic Settings Q 2 =1.0: 1-pass 2.25 GeV beam, measure 1 H, 2 H, 4 He(e,e’p) Q 2 =1.0: 1-pass 2.25 GeV beam, measure 1 H, 2 H, 4 He(e,e’p) Approved for 25 days, beam currents 25-75 μA Approved for 25 days, beam currents 25-75 μA Q 2 =1.8: 2-pass 4.40 GeV beam, measure 1 H, 4 He(e,e’p) Q 2 =1.8: 2-pass 4.40 GeV beam, measure 1 H, 4 He(e,e’p) Approved for 12.4 days, 75 μA Approved for 12.4 days, 75 μA Scattered electron in SHMS in undemanding kinematics: Scattered electron in SHMS in undemanding kinematics: 1.68<P SHMS <3.44 GeV/c19.85 o < θ SHMS <29.75 o Hall C Focal Plane Polarimeter in HMS: Hall C Focal Plane Polarimeter in HMS: 0.83<P HMS <1.15 GeV/c43.99 o < θ HMS <57.42 o HMS(proton) SHMS(electron) HMS FPP

4. Dr. Garth Huber, Dept. of Physics, Univ. of Regina, Regina, SK S4S0A2, Canada. 4 1 H(e,e’p) Scans a Key Part of the Experiment Colors indicate 7 different HMS settings in each scan.Colors indicate 7 different HMS settings in each scan. SHMS setting could also be varied to give good coverage for optics checks.SHMS setting could also be varied to give good coverage for optics checks. Coincidence scans at both Q 2 =1.0, 1.8 (GeV/c) 2. Coincidence scans at both Q 2 =1.0, 1.8 (GeV/c) 2. Scans allow instrumental asymmetries of FPP to be studied, and provide a reference for the polarization-transfer ratios. Scans allow instrumental asymmetries of FPP to be studied, and provide a reference for the polarization-transfer ratios. The e-p coincidence data could also be extremely useful for understanding the SHMS optics, detector & trigger efficiencies. The e-p coincidence data could also be extremely useful for understanding the SHMS optics, detector & trigger efficiencies. HMS (p) SHMS (e’)

5. Dr. Garth Huber, Dept. of Physics, Univ. of Regina, Regina, SK S4S0A2, Canada. 5 Our Contributions to Construction/Commissioning Construction: GH building SHMS Heavy Gas Cerenkov. GH building SHMS Heavy Gas Cerenkov.Commissioning: General assistance with Hall C commissioning, manpower. General assistance with Hall C commissioning, manpower. We will in addition help the Hall C Collaboration understand the SHMS optics, coincidence trigger, and detector efficiencies through the analysis of our data (particularly the 1 H(e,e’p) elastic coincidence scans). We will in addition help the Hall C Collaboration understand the SHMS optics, coincidence trigger, and detector efficiencies through the analysis of our data (particularly the 1 H(e,e’p) elastic coincidence scans). We are open to inviting additional hall users and staff to participate in the experiment. → Already working with Gep Collaboration

6. Dr. Garth Huber, Dept. of Physics, Univ. of Regina, Regina, SK S4S0A2, Canada. 6 Because of low proton momentum in the HMS, need thinner CH 2 analyzers for some kinematic settings. Because of low proton momentum in the HMS, need thinner CH 2 analyzers for some kinematic settings. S0 scintillator which replaced S2 in Gep-III is also not optimal. S0 scintillator which replaced S2 in Gep-III is also not optimal. covers too little of HMS focal plane and increases multiple scattering. covers too little of HMS focal plane and increases multiple scattering. Readiness: Planned work on FPP CH 2 Analyzers Will provide efficient triggering across focal plane while preserving Will provide efficient triggering across focal plane while preserving good missing mass resolution. Improved triggering also desirable for other FPP experiments. Improved triggering also desirable for other FPP experiments. A straightforward project expected to take ~6 months. A straightforward project expected to take ~6 months. Plan new FPP analyzers: Plan new FPP analyzers: Each FPP analyzer will consist of two removable 20cm CH2 layers, and a 5cm scintillator layer. Each FPP analyzer will consist of two removable 20cm CH2 layers, and a 5cm scintillator layer. Can restack existing CH2, but need 8 scintillator bars for each layer. Can restack existing CH2, but need 8 scintillator bars for each layer.

7. Dr. Garth Huber, Dept. of Physics, Univ. of Regina, Regina, SK S4S0A2, Canada. 7 Double Ratio Experiment insensitive to absolute flux uncertainties (luminosity, global detector efficiencies, solid angles) Double Ratio Experiment insensitive to absolute flux uncertainties (luminosity, global detector efficiencies, solid angles) Our `signal’ is the modulation of φ-distribution relative to flat, unpolarized baseline Our `signal’ is the modulation of φ-distribution relative to flat, unpolarized baseline A Potential Commissioning Experiment SHMS optics requirements not particularly demanding : SHMS optics requirements not particularly demanding : p(e,e’p) coincidences easier to understand than single arm (e,e’) p(e,e’p) coincidences easier to understand than single arm (e,e’) Only need SHMS to determine q-vector to 5mrad to know P ’x to 1%. Only need SHMS to determine q-vector to 5mrad to know P ’x to 1%. SHMS settings: SHMS settings: P 19 o Missing mass resolution requirements are modest Missing mass resolution requirements are modest π0π0π0π0

8. Dr. Garth Huber, Dept. of Physics, Univ. of Regina, Regina, SK S4S0A2, Canada. 8 Broader Benefits to Hall C Although our experiment is able to meet its physics goals without a detailed knowledge of detector efficiencies and electron spectrometer optics, the data we acquire will be very useful for the calibration of those experiments to follow. Although our experiment is able to meet its physics goals without a detailed knowledge of detector efficiencies and electron spectrometer optics, the data we acquire will be very useful for the calibration of those experiments to follow. Detailed scans needed to determine FPP instrumental asymmetries very useful for: Detailed scans needed to determine FPP instrumental asymmetries very useful for: Debugging SHMS+HMS coincidence trigger. Debugging SHMS+HMS coincidence trigger. Determining SHMS detection efficiencies (both global and local). Determining SHMS detection efficiencies (both global and local). Can we reproduce previously measured cross sections? Can we reproduce previously measured cross sections? For similar reasons, an experiment was one of the HRS 2 commissioning experiments in Hall A. For similar reasons, an experiment was one of the HRS 2 commissioning experiments in Hall A.

9. Dr. Garth Huber, Dept. of Physics, Univ. of Regina, Regina, SK S4S0A2, Canada. 9 Pros Cons Polarization transfer technique insensitive to most errors. Polarization transfer technique insensitive to most errors. 1 H(e,e’p) coincidence scans useful for detailed determination of SHMS optics, efficiencies, etc. 1 H(e,e’p) coincidence scans useful for detailed determination of SHMS optics, efficiencies, etc. We desire 1-2 pass beam, which is otherwise undersubscribed. We desire 1-2 pass beam, which is otherwise undersubscribed. Scheduling flexiblity: Scheduling flexiblity: Since Q 2 =1.0, 1.8 measurements have separate hydrogen elastics scans, they do not need to be run consecutively. Since Q 2 =1.0, 1.8 measurements have separate hydrogen elastics scans, they do not need to be run consecutively. Don’t even need to keep FPP in HMS between the two runs. Don’t even need to keep FPP in HMS between the two runs. Require installation of FPP in HMS, with straightforward modifications to optimize the FPP analyzers for low momentum. Require installation of FPP in HMS, with straightforward modifications to optimize the FPP analyzers for low momentum. Otherwise, the experiment is relatively simple, with little concern that the experiment cannot run early. Otherwise, the experiment is relatively simple, with little concern that the experiment cannot run early.

10. Dr. Garth Huber, Dept. of Physics, Univ. of Regina, Regina, SK S4S0A2, Canada. 10

11. Dr. Garth Huber, Dept. of Physics, Univ. of Regina, Regina, SK S4S0A2, Canada. 11 4 He(e,e’p) 3 H Q 2 Distribution Polarization-transfer data effectively described by in-medium electromagnetic form factors or charge- exchange FSI. Polarization-transfer data effectively described by in-medium electromagnetic form factors or charge- exchange FSI. For Q 2 ≥1.3 GeV 2 Madrid RWDIA and Schiavilla (2010) results seem to agree. For Q 2 ≥1.3 GeV 2 Madrid RWDIA and Schiavilla (2010) results seem to agree. Our data will allow the precision of the polarization double ratios at Q2=1.0, 1.8 to be greatly improved. Our data will allow the precision of the polarization double ratios at Q2=1.0, 1.8 to be greatly improved. Will R be reduced by 7% with respect to Madrid RWDIA / Schiavilla? Will R be reduced by 7% with respect to Madrid RWDIA / Schiavilla? ≈7%

12. Dr. Garth Huber, Dept. of Physics, Univ. of Regina, Regina, SK S4S0A2, Canada. 12 Compare knock-out from 4 He and 2 H Compare 4 He(e,e’p) 3 H and 2 H(e,e’p)n Double Ratios Compare 4 He(e,e’p) 3 H and 2 H(e,e’p)n Double Ratios Previous 2 H data (Δ) are suggestively close to virtuality dependence of 4 He (○) data. Previous 2 H data (Δ) are suggestively close to virtuality dependence of 4 He (○) data. Modern, rigorous 2 H(e,e’p)n calculations including rescattering effects available. Modern, rigorous 2 H(e,e’p)n calculations including rescattering effects available. Reaction-dynamics effects and FSI will change the ratio up to 5- 8% in this kinematics Reaction-dynamics effects and FSI will change the ratio up to 5- 8% in this kinematics Any larger effects (35%?) should be attributed to something else… Any larger effects (35%?) should be attributed to something else… Medium Effect (QMC) 35% 4% ?

13. Dr. Garth Huber, Dept. of Physics, Univ. of Regina, Regina, SK S4S0A2, Canada. 13 Broad 4 He(e,e’p) Virtuality Coverage Probe the expected strong dependence of medium effects on the momentum of the bound nucleon Probe the expected strong dependence of medium effects on the momentum of the bound nucleon Significant improvement over previous data Significant improvement over previous data Q 2 =1.0 GeV 2 Q 2 =1.0 GeV 2 Parallel kinematics Parallel kinematics p m =0, 140, 220 MeV/c p m =0, 140, 220 MeV/c Scan emphasizes x>1 region, to reduce inelastic channels and probe genuine quasielastic scattering Scan emphasizes x>1 region, to reduce inelastic channels and probe genuine quasielastic scattering Medium Effect (QMC) 35% 4% Proton off-shellness can be quantified via the nucleon virtuality

14. Dr. Garth Huber, Dept. of Physics, Univ. of Regina, Regina, SK S4S0A2, Canada. 14Kinematics Quasielastic scattering Quasielastic scattering Parallel kinematics Parallel kinematics x>1, spectator forward to reduce inelastic channels and probe genuine quasielastic scattering x>1, spectator forward to reduce inelastic channels and probe genuine quasielastic scattering The off-shellness can be quantified as the nucleon virtuality: The off-shellness can be quantified as the nucleon virtuality: Nucleon virtuality is a function of the nucleon momentum only. Nucleon virtuality is a function of the nucleon momentum only. INITIAL STATE: FINAL STATE: 3H3H p 4 He Q 2 (GeV 2 ) p m (MeV/c)Targets1.0 0, +140, +220 4 He, 2 H, 1 H 1.80 4 He, 1 H