Extraction of P[sub 11] Resonance from πN Data and Its Stability

We address a question about how much resonance poles and residues extracted from data depend on a model used for the extraction, and on the precision of data. We focus on the P 11 πN scattering and use the dynamical coupled‐channel (DCC) model developed in Excited Baryon Analysis Center (EBAC) at JLab. We examine the model‐dependence of the poles by varying parameters largely within the EBAC‐DCC model. We find that two poles associated with the Roper resonance are fairly stable against the variation. We also study the stability of the Roper poles against different analytic structure of the P 11 amplitude below πN threshold by using a bare nucleon model. We again find a good stability of the Roper poles.