P_11 Resonance Extracted from pi-N Data and Its Stability

TL;DR

This paper investigates the stability of resonance poles, especially the Roper resonance, in pi-N scattering data using a dynamical coupled-channels model, finding that certain poles are stable despite parameter variations.

Contribution

It demonstrates the stability of Roper resonance poles within a dynamical coupled-channels framework, even when parameters are varied significantly.

Findings

Two Roper poles are stable against parameter variations.

The number of higher-energy poles varies with parameter fitting.

The Roper poles remain stable in a model with a dressed bare nucleon.

Abstract

We study the stability of resonance poles in pi-N P_11 partial wave, particularly the Roper resonance, by varying parameters significantly within the EBAC dynamical coupled-channels model, keeping a good fit to the empirical amplitude. We find that two Roper poles are stable against the variation. However, for higher energies, the number of poles can change depending on how the parameters are fitted within error bars. We also developed a model with a bare nucleon which forms the physical nucleon by being dressed by the meson-cloud. We still find a good stability of the Roper poles.