Multipole Analyses for p(gamma,pi) and p(gamma,gamma) in the region of the P33 delta Resonance

Abstract

Multipole analyses of the p(g,pi0), p(g,pi+) and p(g,g) reactions are carried out using different data sets. With sufficient constraints from polarization observables, the ratio of E2/M1 transition amplitudes for N->delta (EMR) appears to be largely insensitive to differences between recent p(g,pi0) cross section measurements. We deduce a current best estimate of EMR = -(2.85 +/-0.34 +/-0.21)%. Back angle Compton cross sections require a value for the backward spin polarizability that is significantly lower than previous expectations, with a magnitude that is coupled to the (g,pi) cross sections.