FIZIKA B 20 (2011) 2, 149-160

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for the Jefferson Lab Hall A Collaboration
aUniversity of South Carolina, Columbia, SC 29208, U. S. A.
bDuke University, Durham, NC 27708, U. S. A.

Received 18 December 2010;    Accepted 7 December 2011
Online 26 January 2012

Nucleon properties are modified in the nuclear medium. To understand these modifications and their origin is a central issue in nuclear physics. For example, a wide variety of QCD-based models, including quark-meson coupling and chiral-quark soliton models, predict that the nuclear constituents change properties with increasing density. These changes are predicted to lead to observable changes in the nucleon structure functions and electromagnetic form factors. We present results from a series of recent experiments at MAMI and Jefferson Lab, which measured the proton recoil polarization in the 4He (e,e′p )3H reaction to test these predictions. These results, with the most precise data at Q2 = 0.8 (GeV/c)2 and at 1.3 (GeV/c)2 from E03-104, put strong constraints on available model calculations, such that below Q2 = 1.3 (GeV/c)2 the measured ratios of polarization-transfer are successfully described in a fully relativistic calculation when including a medium modification of the proton form factors or, alternatively, by strong charge-exchange final-state interactions. We also discuss possible extensions of these studies with measurements of the 4He(e,e′p )3H and 2H(e,e′p )n reactions as well as with the neutron knockout in 4He(e,e′n )3He.

PACS numbers: 24.70.+s, 25.30.Fj
UDC 539.171, 539.142

Keywords: nucleon in nuclear medium, nucleon structure functions, electromagnetic form factors, proton recoil polarization in (e,e′) reactions

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