1. Understanding the 3 He Nuclei: Asymmetry Measurements in Quasi- Elastic Ge Jin University of Virginia For the E05-102 Collaboration

2. Physics motivation  Only 3 He experiment aiming at studying 3 He itself  A variety of 3 He based experiments seeking to extract neutron information rely on a theoretical knowledge of the ground state spin structure of 3 He  There are three dominant components in the ground-state wave-function (S, D and S’). Understanding the role of the S’ and D states helps us understand the “standard model” of few-body systems  Double polarization measurements have large sensitivities to both (S’ and D) components

4. target in related experiments  Quasi-elastic scattering: to measure neutron electromagnetic form factors  Deep inelastic scattering (DIS): to probe polarized nucleon spin structure functions  In E99-117 experiment (Deep inelastic neutron asymmetry measurement at large Bjorken x), aside from statistical uncertainty, the leading error is comparable to the uncertainty of polarization of the neutron and proton

6. 3 He Asymmetry sensitive to S’ and D waves (theoretical calculation)

7. Non-zero asymmetries, Ax and Az

8. Parasitic measurement of  Quasi-elastic 3 He(e,e’n)pp process  High precision Q 2 =0.41 and 0.51 (GeV/c) 2 for free

9. Experimental Set-up  Beam energy 2.4 GeV  Electron scattering angle of 14.5 and 12.5 deg  Q 2 = 0.35 [GeV/c] 2 and 0.26 [GeV/c] 2  BigBite at 75 and 82 deg, detecting particles with momenta of 200-900(MeV/c)  Neutron detector 62.5 degrees  Beam helicity fast-flipped (30Hz)  Target polarization around 60%

10. Hall A ARC Compton Polarimeter Raster BCM eP Møller Polarimeter Polarized 3 He Target BPM Wire Chambers Trigger Plane (Scintillators ) Neutron Arm Preshower Shower VDCs Q Q Q D Scintillators Gas Cerenkov Pion Rejectors (Pb Glass) Beam Dump Left HRS Right HRSBigBite D

11. High-resolution spectrometers (HRS)  Detects scattering electrons with high resolution  Angular resolution: ~0.6mr in non-dispersive plane ~0.2mr in dispersive plane  Momentum acceptance: ±4.5%  Angular acceptance: ~22mr in non-dispersive plane ~60mr in dispersive plane

12. BigBite spectrometer  Detects protons and deuterons with large acceptance and relatively low resolution  Solid angle of 96 msr  Momentum acceptance: 200-900MeV/c  Two wire chambers (12 wire planes) and two scintillator planes

14. BigBite optics

15. Target polarization

16. Separating protons and deuterons  1.2% deuterons and rest are protons

17. Protons and deuterons in dE-E plot

18. Summary  Thesis students: G. Jin (Uni. Of Virginia), M. Mihovilovic (Uni. Of Ljubljana), E. Long (Kent State Uni.)  Collected abundant data  Analysis ready to go  http://hallaweb.jlab.org/experiment/ E05-102/