Microscopic calculation of the longitudinal response of nuclear matter

The orthogonalized version of correlated basis theory is used to evaluate the longitudinal response of nuclear matter from realistic nuclear interaction. The correlated 1p1h excited states have been fully retained in the calculation. The 2p2h correlated states entering the self-energy insertions, have also been treated exactly. The calculated response results to be in good agreement with previous similar calculations of the density response of symmetrical nuclear matter which included the effect of 2p2h correlated states approximately via the optical potential. Its comparison with the response calculated along the Brueckner theory in the γ-scaling region is also discussed. At moderately high values of the momentum transfer, the longitudinal response is compared with the available experimental data from quasi-free electron scattering off medium-heavy nuclei. Our theoretical estimates are in fair agreement with the data on 40Ca, 48Ca, 56Fe and 238U, except at the highest values of both the momentum transfer and missing energy. (orig.)