Pion photoproduction in a dynamical coupled-channels model

TL;DR

This paper develops a dynamical coupled-channels model for pion photoproduction, accurately describing experimental cross sections and asymmetries up to 1.65 GeV by incorporating hadronic interactions and ensuring gauge invariance.

Contribution

It introduces a gauge-invariant dynamical coupled-channels approach for pion photoproduction based on the Haberzettl et al. formulation, integrating the Juelich pi-N model for hadronic interactions.

Findings

Good agreement with experimental differential cross sections

Accurate photon spin asymmetries up to 1.65 GeV

Model successfully describes multiple pion photoproduction channels

Abstract

The charged and neutral pion photoproduction reactions are investigated in a dynamical coupled-channels approach based on the formulation of Haberzettl, Huang, and Nakayama [Phys. Rev. C 83, 065502 (2011)]. The hadronic final-state interaction is provided by the Juelich pi-N model, which includes the channels pi-N and eta-N comprising stable hadrons as well as the effective pi-pi-N channels pi-Delta, sigma-N, and rho-N. This hadronic model has been quite successful in describing pi-N to pi-N scattering for center-of-mass energies up to 1.9 GeV. By construction, the full pion photoproduction current satisfies the generalized Ward-Takahashi identity and thus is gauge invariant as a matter of course. The calculated differential cross sections and photon spin asymmetries up to 1.65 GeV center-of-mass energy for the reactions gamma p to pi+ n, gamma p to pi0 p, gamma n to pi- p and gamma n to pi0 n are in good agreement with the experimental data.