S-wave $π$-Nucleus Repulsion and Dirac Phenomenology

Abstract

A relativistic $π$-nucleon potential is extended to $m^* \neq m$ to investigate the possibility of generating s-wave $π$-nucleus repulsion. We find that relativity does indeed generate significant repulsion, the exact amount depending on the details of the calculation. In contradistinction the $tρ$ approximation gives very little repulsion.