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arXiv · 1210.4450

Improved description of the $πN$-scattering phenomenology in covariant baryon chiral perturbation theory

J. M. Alarcón·J. Martin Camalich·J. A. Oller
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Abstract

We present a novel analysis of the $πN$ scattering amplitude in covariant baryon chiral perturbation theory up to ${\cal O}(p^3)$ within the extended-on-mass-shell renormalization scheme and including the $Δ(1232)$ explicitly in the $δ$-counting. We take the hadronic phase shifts provided by partial wave analyses as basic experimental information to fix the low-energy constants. Subsequently, we study in detail the various observables and low-energy theorems related to the $πN$ scattering amplitude. In particular, we discuss the results and chiral expansion of the phase shifts, the threshold coefficients, the Goldberger-Treiman relation, the pion-nucleon sigma term and the extrapolation onto the subthreshold region. The chiral representation of the amplitude in the theory with the $Δ$ presents a good convergence from very low energies in the subthreshold region up to energies well above threshold, leading also to a phenomenological description perfectly consistent with the one reported by the respective partial wave analyses and independent determinations. We conclude that a model-independent and systematic framework to analyze $πN$-scattering observables using directly experimental data shall be possible in covariant baryon chiral perturbation theory.

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J. M. Alarcón, J. Martin Camalich, J. A. Oller. 2012-10-16. Improved description of the $πN$-scattering phenomenology in covariant baryon chiral perturbation theory. https://doi.org/10.1016/j.aop.2013.06.001

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