Dynamical coupled-channels model of πN scattering in the W⩽2 GeV nucleon resonance region

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-channels 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 πΔ,ρN, and σN resonant components. The nonresonant 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→π⁰n 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.