Double and single pion photoproduction within a dynamical coupled-channels model

Abstract

Within a dynamical coupled-channels model that has already been fixed by analyzing the data of the $\ensuremath{\pi}N\ensuremath{\rightarrow}\ensuremath{\pi}N$ and $\ensuremath{\gamma}N\ensuremath{\rightarrow}\ensuremath{\pi}N$ reactions, we present the predicted double pion photoproduction cross sections up to the second resonance region, $Wl1.7$ GeV. The roles played by the different mechanisms within our model in determining both the single and double pion photoproduction reactions are analyzed, focusing on the effects attributable to the direct $\ensuremath{\gamma}N\ensuremath{\rightarrow}\ensuremath{\pi}\ensuremath{\pi}N$ mechanism, the interplay between the resonant and nonresonant amplitudes, and the coupled-channels effects. The model parameters that can be determined most effectively in the combined studies of both the single and double pion photoproduction data are identified for future studies.