Stability of P11 Resonance Extracted from pi-N Data

TL;DR

This study investigates the stability of P11 resonance poles in pi-N scattering data, showing that the Roper resonance poles are robust against model variations and different analytic structures.

Contribution

It demonstrates the model- and analytic-structure independence of the Roper resonance poles within the dynamical coupled-channel framework.

Findings

Roper resonance poles are stable against model parameter variations.

Roper poles remain stable under different analytic structures of the amplitude.

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

Abstract

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 P11 pi-N 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 P11 amplitude below pi-N threshold by using a bare nucleon model. We again find a good stability of the Roper poles.