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.
13
14
Preliminary
15