Mesonic exchange current contribution to K+ nucleus scattering

A microscopical many-body calculation of the self-energy of a positive kaon interacting with a nucleus is carried out for kinetic energies TK up to 500 MeV. On top of well known contribution of the impulse approximation, we have considered the kaon coupling to the pions in the nucleus. Previous approximations for the pionic cloud contribution, specially on the imaginary part, are shown to be inadequate. We also find and evaluate new contributions to the imaginary part from the pionic cloud which were not previously considered. The results for the total and differential cross sections are satisfactory after these new contributions are included, but uncertainties remain in the real part. (author). (author). 12 refs, 6 figs