Semirelativistic meson-exchange currents in (e,e) and (e,e' p) reactions

Abstract

Electron-induced one-nucleon knockout observables are computed for a moderate to high momentum transfer, making use of semirelativistic expressions for the one-body and two-body meson-exchange current matrix elements. Emphasis is laid on the semirelativistic form of the D-isobar exchange current and several prescriptions for the dynamical-equivalent form of the D propagator are analyzed. To this end, the inclusive transverse response function, evaluated within the context of the semi-relativistic approach and using different prescriptions for the D propagator, is compared the relativistic Fermi gas model. It is found that the best approximation corresponds to the one using the traditional static D propagator. These semirelativistic approaches, which contain important aspects of relativity, are implemented in a distorted-wave analysis of quasielastic (e,e'p) reactions. Final state interactions are incorporated through a phenomenological optical potential model and relativistic kinematics is assumed when calculating the energy of the ejected nucleon. The results indicate that the meson-exchange currents may modify substantially the TL asymmetry for high missing momentum.