Photocouplings at the pole from pion photoproduction

Abstract

The reactions γp → π 0 p and γp → π + n are analyzed in a semi-phenomenological approach up to E ∼ 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 πN scattering and the world data base of the reactions πN → ηN , KΛ, and KΣ 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.

Light-Quark Baryon Spectroscopy from ANL-Osaka Dynamical Coupled-Channels Analysis

“…5, the mass spectra for the N * and ∆ * resonances extracted by multichannel analysis groups are presented. Our spectrum [8] shown in red are compared with the ones extracted by the Jülich group in 2013 (blue) [9] and the Bonn-Gatchina group in 2012 (green) [6], and also with the four-and three-star resonances assigned by PDG [19]. The results show that the existence and mass values of low-lying resonances have been well determined for most of the spin-parity states.…”

“…[6,7]) and the dynamical-model approaches (e.g., Refs. [8][9][10]), and they have successfully extracted the parameters (complex pole masses and residues, etc.) associated with N * and ∆ * resonances defined by poles of scattering amplitudes.…”

“…Thus establishing the spectrum of high-mass resonances will be a next important task in the N * and ∆ * spectroscopy. Here it is noted that the Jülich group has updated their mass spectrum recently, and it [8], (Blue) Jülich [9], and (Green) Bonn-Gatchina [6]. The spectrum of four-and three-star resonances rated by PDG [19] is also presented with the red and blue filled squares, respectively, of which the length in the longitudinal direction represents the range of the real parts of the resonance pole masses assigned by PDG.…”

Baryons as relativistic three-quark bound states

“…Among those are the Sato-Lee model [70], which has been extended by the EBAC [71][72][73] and ANL/Osaka collaborations [74] and extensively applied to analyze pion photo-and electroproduction data. The Dubna-Mainz-Taiwan (DMT) [75,76], Valencia [77], Jülich-Bonn [78,79] and GSI models [80][81][82] have been developed along similar lines. Theoretical constraints like unitarity and analyticity of the S-matrix are manifest in these approaches.…”

Analysis Tools for Next-Generation Hadron Spectroscopy Experiments

“…Several analysis tools have been developed for the analysis of excited baryons, among them the so-called dynamical coupled-channel approaches, pursued in the ANL-Osaka (former EBAC) collaboration, in the Jülich-Athens-GWU collaboration, in the Dubna-Mainz-Taipeh (DMT) group, and others [139][140][141][142]; see Fig. 5 for recent results.…”