Quasiparticle Renormalization and Pairing Correlations in Spherical Superfluid Nuclei

We present a detailed discussion of the solution of Nambu-Gor'kov equations in superfluid nuclei, which provide a consistent framework to deal with the interplay between particle-hole and particle- particle channel, including the effects of the fragmentation of the quasiparticle strength and of the pairing interaction induced by the exchange of collective vibrations. The coupling between quasiparticle and vibrations is determined from the experimental polarizability of the low-lying collective surface vibrations. This coupling is used to renormalize the properties of quasiparticles obtained from a BCS calculation using the bare nucleon-nucleon interaction. We apply the formalism to the case of the nucleus 120Sn, showing results for the low-energy spectrum and the quasiparticle strength distribution in neighbouring odd nuclei and for the neutron pairing gap.