A number projected model with generalized pairing interaction

Abstract

A mean-field model with a generalized pairing interaction that accounts for neutron–proton pairing is presented. Both the BCS as well as number-projected solutions of the model are presented. For the latter case the Lipkin–Nogami projection technique was extended to encompass the case of nonseparable proton–neutron systems. The influence of the projection on various pairing phases is discussed. In particular, it is shown that number-projection allows for mixing of different pairing phases but, simultanously, acts destructively on the proton–neutron correlations. The basic implications of proton–neutron pairing correlations on nuclear masses are discussed. It is shown that these correlations may provide a natural microscopic explanation of the Wigner energy lacking in mean-field models. A possible phase transition from isovector to isoscalar pairing condensate at high angular momenta is also discussed. In particular predictions for the dynamical moments of inertia for the superdeformed band in 88Ru are given.