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.