Dynamical coupled-channels model ofπNscattering in theW⩽2GeV nucleon resonance region

Abstract

As a first step to analyze the electromagnetic meson production reactions in the nucleon resonance region, the parameters of the hadronic interactions of a dynamical coupled-channel model, developed in Physics Reports 439, 193 (2007), are determined by fitting the πN scattering data. The channels included in the calculations are πN , ηN and ππN which has π∆, ρN , and σN resonant components. The non-resonant meson-baryon interactions of the model are derived from a set of Lagrangians by using a unitary transformation method. One or two bare excited nucleon states in each of S, P , D, and F partial waves are included to generate the resonant amplitudes in the fits. The parameters of the model are first determined by fitting as much as possible the empirical πN elastic scattering amplitudes of SAID up to 2 GeV. We then refine and confirm the resulting parameters by directly comparing the predicted differential cross section and target polarization asymmetry with the original data of the elastic π ± p → π ± p and charge-exchange π − p → π 0 n processes. The predicted total cross sections of πN reactions and πN → ηN reactions are also in good agreement with the data. Applications of the constructed model in analyzing the electromagnetic meson production data as well as the future developments are discussed.

Impact ofπN→ππNdata on determining high-mass nucleon resonances

“…[8]. As a comparison, we also present the prediction of our early DCC model [2,10] (the green dotted curves), in which the amplitudes are unitary in the πN, ηN, and ππN(π∆, σN, ρN) channel space and are determined by analyzing the πN → πN scattering up to W = 2 GeV. Even without any adjustment of the model parameters to the πN → ππN data, our models reproduce the available total-cross-section data to better than ∼ 20% (∼ 60%) accuracy at W < 1.6 GeV (W > 1.6 GeV).…”

Baryons as relativistic three-quark bound states

“…2.6 is solved in dynamical coupled-channel models which also take into account the dispersive parts from intermediate channels. 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.…”

Modern Dynamical Coupled-Channels Calculations for Extracting and Understanding the Nucleon Spectrum

“…Figure 3 shows pole positions of P 11 N * resonances extracted from a dynamical model developed in Ref. [12]. Here, the poles A and B are well known as the double-pole (pole and shadow-pole [13]) structure of the Roper resonance with respect to the π∆ channel, which has been observed also in Refs.…”

“…Then it was found that within the model developed in Ref. [12], all of the presented three P 11 resonance poles (the poles A, B, C) are generated from this single bare state as a result of its coupling to the multireaction channels [13]. This implies that a naïve one-to-one correspondence between the physical resonances and the baryons within static hadron models, within which the dynamical effects originating from coupling to the reaction channels are neglected, does not exist in general.…”