Isospin decomposition of $\gamma N \to N^*$ transitions within a dynamical coupled-channels model

TL;DR

This paper extends a dynamical coupled-channels model to include neutron photoproduction data, enabling isospin decomposition of gamma N to N* transitions, which aids in testing hadron structure models and neutrino reaction modeling.

Contribution

It introduces an extended analysis incorporating neutron data into the coupled-channels model, providing new isospin-decomposed transition amplitudes for N* resonances.

Findings

Determined gamma n --> N* transition amplitudes at resonance poles.

Revised resonance pole positions and gamma p --> N* amplitudes.

Provided isospin decomposition of transition amplitudes.

Abstract

By extending the dynamical coupled-channels analysis performed in our previous work [Phys. Rev. C 88, 035209 (2013)] to include the available data of photoproduction of pi meson off the neutron, the transition amplitudes for the photo-excitation of the neutron to nucleon resonances, gamma n --> N*, at the resonance pole positions are determined. The combined fits to the data for both the proton- and neutron-target reactions also revise our results for the resonance pole positions and the gamma p --> N* transition amplitudes. Our results allow an isospin decomposition of the gamma N --> N* transition amplitudes for the isospin I=1/2 N* resonances, which is necessary for testing hadron structure models and gives crucial inputs for constructing models of neutrino-induced reactions in the nucleon resonance region.