P11 πN scattering in a potential model and in the cloudy bag model

We discuss P11 πN scattering in a model where the π is coupled to quark bags for baryons N,Nsup(*), Δ. From the underlying qqπ couplings we derive B'Bπ vertices which are used in a solution of a πN, πΔ two-channel scattering problem. Using one bagradius from a fit to P33 πN data, we are unable to reproduce delta11 which requires a Roper radius Rsub(R)>Rsub(N). We discuss the sensitivity of the fit to small variations in other bag parameters. The theory is compared with a simple potential model and with field theories employjng baryons instead of quark fjelds. (author)