Extraction of P11 resonances from πN data

We show that two P11 nucleon resonance poles near the πΔ threshold, obtained in several analyses, are stable against large variations of parameters within a dynamical coupled-channels analysis based on meson-exchange mechanisms. By also performing an analysis based on a model with a bare nucleon state, we find that this two-pole structure is insensitive to the analytic structure of the amplitude in the region below the πN threshold. Our results are Mpole=(1363-6+9-i79-5+3) and (1373-10+12-i114-9+14) MeV. We also demonstrate that the number of poles in the 1.5-GeV ≤W≤ 2-GeV region could be more than one, depending on how the structure of the single-energy solution of SAID is fitted. For three-pole solutions, our best estimated result of a pole near N(1710) listed by Particle Data Group is (1829-65+131-i192-110+88) MeV, which is close to the results of several previous analyses. Our results indicate the need for more accurate πN reaction data in the W> 1.6-GeV region for high-precision resonance extractions.