Pion photoproduction in a dynamical coupled-channels model

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.Comment: revtex4-1, 26 pages, 6 tables, 21 figure

Eta photoproduction in a combined analysis of pion- and photon-induced reactions

“…The extension of the Jülich approach to pion photoproduction in a field-theoretical formulation, that respects the generalized off-shell WardTakahashi identity, was achieved in Ref. [54]. In Ref.…”

“…[54]. In this study an earlier version of the Jülich model was utilized to provide the hadronic final-state interaction.…”

Resonance Dynamics in Coupled Channels

“…17. Of all results, we would like to stress the importance of gauge invariance as illustrated in Fig.…”

“…The Jülich model [9][10][11][12][13][14][15][16][17] that was subject of the presentation, fulfills analyticity, two-body unitarity and requirements from three-body unitarity, and gauge invariance. In recent updates, the approach was extended to pion photoproduction 17 and the analysis of the reactions π − p → ηn, as illustrated in Fig.…”

“…38,39,40). The dashed curves are obtained by switching off the contact current other than the Kroll-Ruderman term, 17 i.e. those terms that are required to restore gauge invariance.…”