\pi N scattering in relativistic baryon chiral perturbation theory revisited

TL;DR

This paper revisits pion-nucleon scattering analysis using a relativistic chiral perturbation theory framework, achieving comparable low-energy phase shift descriptions and extending the energy range through unitarization.

Contribution

It provides a relativistic covariant analysis of  scattering up to  order, with new low-energy constants and extended energy range via unitarization.

Findings

Accurate low-energy phase shifts up to 1.14 GeV

New determinations of low-energy constants and scattering parameters

Extended energy range for data reproduction through unitarization

Abstract

We have analyzed pion-nucleon scattering using the manifestly relativistic covariant framework of Infrared Regularization up to {\cal O}(q^3) in the chiral expansion, where q is a generic small momentum. We describe the low-energy phase shifts with a similar quality as previously achieved with Heavy Baryon Chiral Perturbation Theory, \sqrt{s}\lesssim1.14 GeV. New values are provided for the {\cal O}(q^2) and {\cal O}(q^3) low-energy constants, which are compared with previous determinations. This is also the case for the scattering lengths and volumes. Finally, we have unitarized the previous amplitudes and as a result the energy range where data are reproduced increases significantly.