Polarization Transfer inH4e(e→,e′p→

Abstract

Polarization observables in the (4)He(e-->,e'p-->)(3)H reaction are calculated using accurate three- and four-nucleon bound-state wave functions, a realistic model for the nuclear electromagnetic current operator, and a treatment of final-state interactions with an optical potential. In contrast to earlier studies, no significant discrepancies are found between theory and experiment both for the ratio of transverse to longitudinal polarization transfers and for the induced polarization, when free-nucleon electromagnetic form factors are used in the current operator. The present results challenge the current interpretation of the experimental data in terms of medium-modified form factors.

Polarization Transfer in theHe4(e→,e′p→)Paolone1, Malace2, Strauch3 et al. 2010Phys. Rev. Lett.9741051View full textAdd to dashboardCite

“…The data are in excellent agreement with model calculations including the medium modification of the proton form factors through the quark-meson coupling model presented by Lu et al [8], and with a chiral quark soliton model by Smith and Miller [14]. A model calculation by Schiavilla [17], which uses conventional free-space nucleon form factors, but employs a different treatment of in-medium nucleon interactions, including charge exchange processes, also agrees with the overall reduction of the polarization-transfer ratios, albeit within large uncertainties. Combining these data with similar precision induced-polarization data, directly sensitive to the amount of in-medium nucleon interactions, may lead to a definite statement in favor or against the effective use of proton medium modifications.…”

“…However, in-medium nucleon interactions complicate this picture, and even raise the question as to whether the concept of medium modifications is a meaningful one, due to the complex nature of the in-medium interaction. Predictions from Schiavilla [17] contend that final-state interactions (FSIs) including charge exchange processes and meson exchange currents lead to a quenching of 10% in the polarizationtransfer ratio P ′ x /P ′ z in the quasielastic scattering reaction 4 He( e, e ′ p ) 3 H compared with the free-space reaction 1 H( e, e ′ p ). The correct treatment of FSIs in a model calculation is essential to separate any unconventional medium effects from FSIs, since both influence the polarization-transfer observables.…”

“…Theoretical calculations from Schiavilla [17] are included in Figure 2 as a grey band, and assume a missing momentum close to zero and have not been acceptance corrected. Schiavilla shows with conventional many-body calculations that a model with free-space nucleon form factors can describe R as a function of Q 2 .…”

“…The curves represent RDWIA (dashed), RD-WIA + QMC (solid), and RDWIA + CQS (dash-dot) calculations with the current operator cc2 and the MRW optical potential [25]. The grey band represents Schiavilla's model [17]; See text for details. [25].…”

Faddeev and Glauber calculations at intermediate energies in a model forn+dscattering

“…Today Glauber amplitudes are widely used to account for final state interactions in (e,e'p) reactions at high and intermediate energies [3,4,5]. Glauber theory is applied to investigate color transparency, in (e, e ′ p) reactions and in the electroproduction of mesons [6,7].…”