Short range effects in nucleon-nucleus scattering

The character of the two-nucleon wave function within the range of the interaction potential is manifested in intermediate energy nucleon-nucleus scattering via off-shell effects and a resulting non-locality of the T operator. I present here a study of the off-shell and non-local behavior of the free nucleon-nucleon T matrix for the RSC and Paris potentials in the energy regime between 100 and 350 MeV. We find the following results: (1) The off-shell amplitudes for the two potentials are strikingly similar, both for the individual partial waves and for the central and spin-orbit parts of the amplitude, despite large differences in the momentum-space matrix elements of the potential. (2) The amplitudes are strongly non-local. (3) Although they are non-local, they are nearly independent of the angle between the vectors k-k' and k+k', and they vary very slowly with energy in the regime considered. This reduces a function of 4 variables to a function of 2. (4) Elastic scattering calculations using the free non-local T operator in an approximate way give results comparable to the Love-Franey Ansatz