Understanding the 3 He Nuclei: Asymmetry Measurements in Quasi- Elastic Ge Jin University of Virginia For the E Collaboration

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

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 E 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

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

Non-zero asymmetries, Ax and Az

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

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 (MeV/c)  Neutron detector 62.5 degrees  Beam helicity fast-flipped (30Hz)  Target polarization around 60%

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

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

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

BigBite optics

Target polarization

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

Protons and deuterons in dE-E plot

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  E05-102/