Pion-nucleon scattering lengths in the cloudy bag model

Abstract

We re-examine pion-nucleon s-wave scattering in the volume coupling version of the CBM. If the effects of multiple scattering are taken into account, one needs some phenomenological repulsive interaction in order to reproduce the experimental data. We parametrize this repulsion as a twenty percent increase in the pion mass inside the bag. It is argued that this relatively small change in mass provides strong, a posteriori support for the original assumptions of the CBM.