Helicity dependence of the γp→Nπ channels and multipole analysis in the Δ region

A high-quality double-polarization data set for the helicity dependence of the total and differential cross-sections for both γp→Nπ channels in the Δ region has been obtained in the framework of the GDH experiment. The experiment, performed at the Mainz microtron MAMI, used a 4 π detection system, a circularly polarized photon beam, and a longitudinally polarized frozen-spin target. These data are included in the database to perform a multipole analysis to determine the properties of the Δ(1232) -resonance. For the resonant Δ(1232) multipoles we find a very good agreement with previous analyses, while the nonresonant ones show significant deviations.