NUCLEAR RESPONSE FUNCTIONS IN QUASI-ELASTIC ELECTRON-SCATTERING

We calculate longitudinal and transverse response functions for quasielastic electron scattering in a relativistic random-phase approximation to the Walecka model. The particle-hole response and the Pauli blocking of nucleon-antinucleon (NN̄) excitations are calculated exactly in the finite system. Vacuum polarization effects are included in a local-density approximation. As the effective nucleon mass decreases virtual NN̄ pairs are more readily excited in the medium. This change in vacuum polarization reduces the proton's effective charge and results in a longitudinal response that is substantially below the Hartree result and in good agreement with experiment. In the Walecka model nucleons interact via the exchange of isoscalar sigma and omega mesons. The transverse response function is dominated by the (mostly) isovector anomalous moment, and is therefore largely unchanged. © 1990.