Can multiple-scattering theory explain the low-energy pion-nucleus interaction?

Abstract

We discuss the 50 MeV data for the elastic scattering of pions by ${}_{}{}^4{}_{}{}^{}\mathrm{He}$ and ${}_{}{}^{12}{}_{}{}^{}\mathrm{C}$ and show that a careful treatment of off-shell effects and the effects of pion absorption, in the context of a multiple-scattering theory, is able to explain the data. We present a discussion of the importance of nuclear binding effects and describe how the Fermi motion influences the calculation of the optical potential. (In this work we have performed a complete integration over the variables which describe the Fermi motion of the target nucleons.) It may be seen from this discussion how the neglect of these features in the fixed scatterer approximation leads to large discrepancies between the results of theoretical calculations and the experimental data.