Nucleon-Nucleon Phase Shifts and Pairing in Neutron Matter and Nuclear Matter

We consider 1S0 pairing in infinite neutron matter and nuclear matter and show that in the lowest order approximation, where the pairing interaction is taken to be the bare nucleon-nucleon (NN) interaction in the 1S0 channel, the pairing interaction and the energy gap can be determined directly from the 1S0 phase shifts. This is due to the almost separable character of the NN interaction in this partial wave. Since the most recent NN interactions are charge-dependent, we have to solve coupled gap equations for proton-proton, neutron-neutron, and neutron-proton pairing in nuclear matter. The results, however, are found to be close to those obtained with charge-independent potentials.