Measurement of Target Single Spin Asymmetry in Quasi-elastic 3He (e, e’)

Bo Zhao

College of William and Mary

For the Hall-A Quasi-elastic collaboration

(Updates on Ay experiment E05-015)

1

Two-photon Exchange progress

l l'

PqP'q

N N'

H

k k'

Pq P'q

k k'

Pq P'q

2

For )'()'()()( pNklpNkl

In terms of GPD moments

A measurement of Ay has sensitivity to GPD model input

Y.C. Chen etc., PRL 93, 122301 (2004)

Target Single Spin Asymmetry (SSA)

3

4

Expected result

-1.35

Theoretical prediction

5

Experimental Facility

6

E0 [GeV]

E’ [GeV]

θlab [Deg]

Q2 [GeV]2

|q| [GeV]

θq

[Deg]

1.25 1.22 17 0.13 0.359 712.43 2.18 17 0.46 0.681 623.61 3.09 17 0.98 0.988 54

This Ay experiment (E05-015) was run from

April 26th to May 12th

The Kinematics of this Ay experiment:

Ay Kinematics

7

Electron Identification

Nphe (ADCs)

Run number 8

Positive target spin

T1 scalar asymmetry between L and R

Negative target spin

Run number

Run number

Positive target spin

Negative target spin

Run number

9

T3 scalar asymmetry between L and R

Run number

Positive target spin

Negative target spin

Run number

10

u3 scalar asymmetry between L and R

11

Preliminary raw SSA

Preliminary

12

Summary and future planPreliminary raw SSA at Q2 = 0.98 is non-zero and consistent between L-arm data and R-arm data. An independent cross-check was being carried by E. Long.

Raw SSA at Q2 = 0.13 and Q2 = 0.46 is almost finished and will be released soon after an independent cross-check.

Target analysis by Y. Zhang was almost completed.

Systematic uncertainty study

Raw SSA 3He SSA neutron SSA with dilution factor, target polarization and so on.

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14

Preliminary

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