Multipole Analyses for p(γ, π) and p(γ, γ) in the Region of the P 33 Δ Resonance

Multipole analyses of the p(γ, π°), p(γ, π+) and p(γ, γ) reactions are carried out using different data sets. With sufficient constraints from polarization observables, the ratio of E2/M1 transition amplitudes for N → Δ (EMR) appears to be largely insensitive to differences between recent p(γ, π°) 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 δπ that is significantly lower than previous expectations, with a magnitude that is coupled to the (γ, π) cross sections.