Spectroscopic factors for nucleon knock-out from 16O at small missing energy.

Spectroscopic factors for one-nucleon knock-out from O are calculated for states with low excitation energy in N with the Bonn-C potential. A method is proposed to deal with both shortand long-range correlations consistently. For this purpose a Green’s function formalism is used and the self-energy in the Dyson equation is approximated as the sum of an energy-dependent Hartree-Fock ~HF! term and dispersion and correlation terms of higher order in the G-matrix interaction. This G matrix is obtained by solving the Bethe-Goldstone equation with a Pauli operator which excludes just the model space treated in the subsequent calculation of the self-energy. The energy dependence of the HF energies induces an additional reduction of the spectroscopic factors for quasiparticle states close to the Fermi level by about 10%. Experimental data may signal the need of some further improvement in the treatment of intermediateand long-range correlations. @S0556-2813~96!04105-2#