Long-range correlations and the momentum distribution in nuclei

Abstract The influence of correlations on the momentum distribution of nucleons in nuclei is evaluated starting from a realistic nucleon-nucleon interaction. The calculations are performed directly for the finite nucleus 16 O making use of the Green function approach. The emphasis is focused on the correlations induced by the excitation modes at low energies described within a model space of shell-model configurations including states up to the sdg shell. Our analysis demonstrates that these long-range correlations do not produce any significant enhancement of the momentum distribution at high missing momenta and low missing energies. This is in agreement with high-resolution ( e, e′ p ) experiments for this nucleus. We also try to simulate the corresponding effects in large nuclei by quenching the energy spacing between single-particle orbits. This yields a sizable enhancement of the spectral function at large momenta and small energy. Such behavior could explain the deviation of the momentum distribution from the mean-field prediction, which has been observed in ( e, e′, p ) experiments on heavy nuclei like 208 Pb.