[Shms_users] New proposal: Recoil polarization in 4He, 2H, and 1H(e, e'p)

[Garth Huber]

Dear Collaborators,

We are preparing a new proposal to measure the proton recoil polarization in 
4He(e,e'p)3H and 2H(e,e'p)n in Hall C. This is an update of our earlier proposal 
PR08-001 and would continue the series of our experiments at MAMI and JLab Hall 
A (E93-049 and E03-104). Key features of the new experiment are:

(1) One new high-precision data point for the 4He polarization-transfer double 
ratio at Q2 = 1.8 GeV2.  Models, constrained to our E03-104 data, using free 
nucleon form factors agree above 1.3 GeV2 while the predicted effect of medium 
modified form factors are as large as 5%.  This data point should put tight 
constraints to possible medium effects.

(2) A significantly improved missing momentum coverage at Q2 = 1.0 GeV2. Here, 
we propose to measure a range almost covering -200 to +300 MeV/c in parallel 
kinematics.  Medium effects are expected to grow with the virtuality of the 
knocked out proton (as do other reaction mechanism effects to which these 
additional data can provide crucial constraints). We will focus on the x > 1 
region to minimize FSI effects.  This missing momentum distribution will give us 
an additional high-precision data point at Q2 = 1.0 GeV2.

(3)  We propose to study the momentum distribution in both, the 4He(e,e'p)3H and 
2H(e,e'p)n reactions to compare knockout data of tightly and weakly bound 
protons.  These data can help answering the question whether medium effects 
depend on the mean nuclear density or rather on the momentum or virtuality of 
the nucleon.

A draft version of the proposal is posted at:

http://www.jlab.org/~strauch/pac37/he4_pac37.pdf

We would like to invite you to join this proposal.  Please let us know.  We 
would appreciate any comments or suggestions you may have regarding this draft. 
If you send your remarks, please, refer to the date on the front page as we keep 
updating the text.  The text is not final, yet.

Sincerely,

Steffen Strauch,
also for Ed Brash, Garth Huber, and Ron Ransome.

-- 
Dr. Garth Huber, Dept. of Physics, Univ. of Regina, Regina, SK S4S0A2, Canada.
tel: 1-306-585-4240. fax: 1-306-585-5659.