Extraction of P11 Resonance from pi-N Data and Its Stability

TL;DR

This paper investigates how the extraction of P11 resonance poles from pi-N scattering data depends on the model and data precision, finding that the Roper resonance poles are notably stable across various models and assumptions.

Contribution

It demonstrates the stability of Roper resonance poles against model variations and different analytic structures in the P11 amplitude, using a dynamical coupled-channel approach.

Findings

Roper resonance poles are stable under model parameter variations.

Stability of Roper poles persists with different analytic structures.

Model dependence of resonance poles is limited for the Roper resonance.

Abstract

An important question about resonance extraction is how much resonance poles and residues extracted from data depend on a model used for the extraction, and on the precision of data. We address this question with the dynamical coupled-channel (DCC) model developed in Excited Baryon Analysis Center (EBAC) at JLab. We focus on the P11 pi-N scattering. We examine the model-dependence of the poles by varying parameters to a large extent within the EBAC-DCC model. We find that two poles associated with the Roper resonance are fairly stable against the variation. We also develop a model with a bare nucleon, thereby examining the stability of the Roper poles against different analytic structure of the P11 amplitude below pi-N threshold. We again find a good stability of the Roper poles.