Baryon resonance extraction from πN data using a unitary multichannel model

A unitary multi-channel approach, first developed by the Carnegie-Mellon Berkeley group, is applied to extract the pole positions, masses, and partial decay widths of nucleon resonances from the partial wave amplitudes for the transitions from πN to eight possible final baryon–meson states. Results of single energy analyses of the VPI group using the most current database are used in this analysis. A proper treatment of threshold effects and channel coupling within the unitarity constraint is shown to be crucial in extracting resonant parameters, especially for the resonance states, such as S11(1535), which have decay thresholds very close to the resonance pole position. The extracted masses and partial decay widths of baryon resonances up to about 2 GeV mass are listed and compared with the results from previous analyses. In many cases, the new results agree with previous analyses. However, some significant differences, in particular for the resonances that are weakly excited in πN reactions, are found.