E05-102: Measurement of A

x and A

z asymmetries in the quasi-elastic 3He(e,e'd) reaction

Hall A Collaboration Meeting

Xiaohui ZhanMIT

prsented by

Measurement of Ax and Az Asymmetries

in the quasi-elastic 3He(e,e'd) reaction

E05-102: Measurement of A

x and A

z asymmetries in the quasi-elastic 3He(e,e'd) reaction

Main Physics Goals

General: Achieve a better understanding of the ground-state spin structure of 3He, i.e. improve our understanding of 3He rather than using it as an effective neutron target.

Specific: Test state-of-the-art Faddeev calculations and use these calculations to gain a better understanding of the dynamics and the S' and D wave-function components of 3He.

This is accomplished by making precision measurementsof the double polarized 3He(e,e'd) reaction.

Impact: All experiments using 3He as a polarized neutron target.

E05-102: Measurement of A

x and A

z asymmetries in the quasi-elastic 3He(e,e'd) reaction

An A1 Example:

Shown are the error bars from a recent Hall A polarized 3He experiment: PRL 92 (2004) 012004.

At 12GeV this measurement becomes limited by our understanding of 3He.

E05-102: Measurement of A

x and A

z asymmetries in the quasi-elastic 3He(e,e'd) reaction

Ground State of 3He

S spatially symmetric, 90% of spin-averaged WF, “neutron target”

D generated by tensor component of NN force, 8.5%

S' mixed-symmetry configuration, 1.5%

As a function of missing momentum, these relative contributions can affect the (e,e'N) reaction differently.

e.g. the NIKHEF D(e,e'p) results: PRL 89 (2002) 102302

E05-102: Measurement of A

x and A

z asymmetries in the quasi-elastic 3He(e,e'd) reaction

Sketch of Experiment

single arm elastic electronquasi-elastic electron

quasi-elastic deuterontarget spin parallel and perpendicular to q

E05-102: Measurement of A

x and A

z asymmetries in the quasi-elastic 3He(e,e'd) reaction

BigBite Spectrometer During SRC Experiment

E05-102: Measurement of A

x and A

z asymmetries in the quasi-elastic 3He(e,e'd) reaction

Bochum/Krakow Group Ingredients

Q2 fixed by HRS and the missing momentum range “bitten” without moving BigBite

E05-102: Measurement of A

x and A

z asymmetries in the quasi-elastic 3He(e,e'd) reaction

Sensitivity to S'

The same technique as used to extract Form Factors from asymmetry data.

E05-102: Measurement of A

x and A

z asymmetries in the quasi-elastic 3He(e,e'd) reaction

Analysis of Proton EventsThese New CPU Intensive Calculations Have Just Become Available

both (e,e'p) and (e,e'd) will be detected in BigBite

proton asymmetry is not sensitive to S' part of the wave-function

E05-102: Measurement of A

x and A

z asymmetries in the quasi-elastic 3He(e,e'd) reaction

Addition of a HANDHall A Neutron Detector

Fully Assembled And Tested

DAQ and Cables Available

A Commitment of Manpower

E05-102: Measurement of A

x and A

z asymmetries in the quasi-elastic 3He(e,e'd) reaction

Measurement of GEn by HAND

Systematics Limited Measurement

Expected Result is Shown with the Conservative Estimate 0.0039

E05-102: Measurement of A

x and A

z asymmetries in the quasi-elastic 3He(e,e'd) reaction

Summary & Status

Standard HRS

BigBite and Neutron Detector PMTs need to be tested

Wirechambers same as will be used for d2 and Transversity

3He system similar to d2 and Transversity

We will take the Benchmark Data at a fixed Q2 in (e,e'd) and (e,e'p) simultaneously over a broad range of missing momentum that the Bochum/Krakow and Hannover groups insist is needed to verify their calculations.

This data will allow significant progress to be made on understanding of the three-body system.

We were approved for 15 PAC days of polarized electrons beams.