Target Single Spin Asymmetries using Vertically Polarized 3 He

Target Single Spin Asymmetries using Vertically Polarized 3He

• Todd Averett—College of William and Mary

• Three experiments will measure these SSA’s• One is running concurrently with transversity• Two others tentatively scheduled for early ‘09.

Unpolarized electron scattering from vertically (normally) polarized 3He.

Three experiments will measure Ay: Quasi-elastic, DIS, and QE 3He(e,e’n).

(Christ-Lee Theorem)

Expected Results

Q2=0.5, 0.75, 1.0 GeV2

New polarized target now achieving 65% in-beam polarization due tohybrid alkali and narrowed lasers.

What about two-photon exchange in inclusive DIS?

• The formalism remains the same:Ay=0 for 1-photon exchange

• For DIS, one assumes that the scattering is dominated by two photon exchange with a single quark.

• For non-interacting quarks, Ay=0 for two-photon exchange!

• Afanasev, Strikman, Weiss (Phys.Rev.D77:014028,2008) predict Ay~10-4 using a model based on the quark transversity distribution.

• This means the SSA should change by two orders of magnitude from DIS to QE kinematics. This is a direct study of the “transition” from hadron-like to parton-like behavior.

• This is being measured in Hall A concurrent with the transversity experiment using BigBite Spectrometer.

• HAPPEX DAQ and Hall A Lumi’s are being used to monitor the luminosity asymmetry. (Joe Katich-WM graduate thesis student)

SSA in quasi-elastic 3He(e,e’n)• By detecting the outgoing neutron, the SSA is sensitive to FSI• PWIA Calculations predict Ay=0• Theoretical models with FSI, 3He wavefunction, etc predict Ay=20-45%• Unpublished measurement at NIKEF measured large Ay~50% at Q2=0.2 GeV2!!!

Laget, Nagorney

Golak