Semirelativistic meson-exchange currents in (e,e′) and (e,e′p) reactions -: art. no. 014604

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 Delta-isobar exchange current and several prescriptions for the dynamical-equivalent form of the Delta 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 Delta propagator, is compared with the fully relativistic calculation performed within the scheme of the relativistic Fermi gas model. It is found that the best approximation corresponds to the one using the traditional static Delta 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.