Unitarized pion-nucleon scattering within Heavy Baryon Chiral Perturbation Theory

TL;DR

This paper applies the Inverse Amplitude Method to unitarize Heavy Baryon Chiral Perturbation Theory pion-nucleon scattering amplitudes, extending their validity and generating the Delta(1232) resonance, with a focus on phase shift description.

Contribution

It introduces a unitarization approach for Heavy Baryon Chiral Perturbation Theory amplitudes that captures resonances and extends applicability.

Findings

Successfully describes pion-nucleon phase shifts

Generates the Delta(1232) resonance

Fits data with various chiral parameter sets

Abstract

By means of the Inverse Amplitude Method we unitarize the elastic pion-nucleon scattering amplitudes obtained from Heavy Baryon Chiral Perturbation Theory to O(q^3). Within this approach we can enlarge their applicability range and generate the Delta(1232) resonance. We can find a reasonable description of the pion nucleon phase shifts with (q^2) parameters in agreement with the resonance saturation hypothesis. However, the uncertainties in the analysis of the low energy data as well as the large number of chiral parameters, which can have strong correlations, allow us to obtain very good fits with rather different sets of chiral constants.