Pion and photon couplings of N* resonances from scattering on the proton

Results of a relativistic model for pion- and photon-induced reactions on the proton are presented. The model is crossing symmetric and gauge invariant. The nucleon resonances P-11(1440), P-11(1710), D-13(1520), S-11(1535), S-11(1650), P-33(1232), P-33(1600), S-31(1620), and D-33(1700) have been included explicitly in the calculation. Unitarity within the channel space pi N circle plus gamma N below the two-pion production threshold has been achieved by using the K-matrix approach. Strong and electromagnetic coupling parameters of the N* resonances have been determined from a fit to the pion-nucleon phase shifts, pion-photoproduction multipoles and Compton-scattering cross sections. The model is shown to describe simultaneously most of the available data. Results for the electric and magnetic polarizabilities of the nucleon are presented