Unitarized pion–nucleon scattering amplitude from inverse amplitude method

Abstract

In a recent work on low energy pion–nucleon scattering, instead of using chiral perturbation theory (ChPT) amplitude, we started from a pion–nucleon soft-pion result and used elastic unitarity directly as a dynamical constraint to construct first-order unitarity corrected amplitudes. The resulting amplitudes are crossing symmetric but, as the ChPT ones, satisfy only approximate unitarity relation. In the present work, we reconsider our approach and we apply the inverse amplitude method (IAM) in order to access the energy resonance region. We present the resulting S- and P-wave phase shifts that are shown to be in qualitative agreement with experimental data.