Many-body correlation effects on the longitudinal response in the quasielastic (e,e’) reaction

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Abstract
A study is made of the influence of many-body corrections on the longitudinal response function for the inclusive quasielastic (e,e’) reaction. This response function is well known to be suppressed, by about a factor of 2, when compared with theoretical predictions based on the concept of single nucleon ejection. This is a characteristic of the data that persists through a wide range of different nuclei and suggests a violation of the Coulomb sum rule. It is shown here how an estimation of the effect of many-body correlations, at large momentum transfers, including a consistent treatment of inelastic final-state interactions, can be computed through a relationship to the nuclear optical model. The approximations are such that the Coulomb sum rule is guaranteed to remain satisfied providing the optical potential is Hermitian analytic. Calculations of the longitudinal response are carried out within the Fermi-gas model using phenomenological parametrizations of the nuclear optical potential. The reductions in both the peak strength and the total integrated response are signficant, but not sufficient to explain the discrepancy between theory and experiment. The resulting distribution of strength is characterized by the energy-weighted sum rule which remains satisfied to the level of the approximations, about 5%.