Photocouplings at the Pole from Pion Photoproduction

Abstract

The reactions $\gamma p\to {\pi }^{0}p$ and $\gamma p\to {\pi }^{+}n$ are analyzed in a semi-phenomenological approach up to $E\sim 2.3$ GeV. Fits to differential cross section and single and double polarization observables are performed. A good overall reproduction of the available photoproduction data is achieved. The Jülich2012 dynamical coupled-channel model -which describes elastic $\pi N$ scattering and the world data base of the reactions $\pi N\to \eta N$, $K\Lambda$, and $K\Sigma$ at the same time - is employed as the hadronic interaction in the final state. The framework guarantees analyticity and, thus, allows for a reliable extraction of resonance parameters in terms of poles and residues. In particular, the photocouplings at the pole can be extracted and are presented.

Comments: 37 pages, 31 figures. Angles of the photocouplings at the pole adapted to the convention of Phys. Rev. C 87, 068201 (2013)