Improved description of the pi N scattering phenomenology in covariant baryon chiral perturbation theory
Jose Manuel Alarcon (KPH Mainz (Theory))

In this talk I will show how covariant baryon chiral perturbation theory (BChPT) achieves the best convergence if one includes the \(\Delta(1232)\)-resonance as an explicit degree of freedom. We show that, within this new framework, we are able to get an improved description of the pion-nucleon scattering phenomenology and to connect, for first time in BChPT, the physical information with information that lies in the subthreshold region. Moreover, we also extract the value of the pion-nucleon sigma term employing experimental information and study the strangeness content on the nucleon derived from the sigma term. I will show how, from this updated determinations of the pion-nucleon sigma term and the strangeness content of the nucleon, a new scenario emerges where the quantities are in good agreement with updated experimental determinations and recent lattice QCD calculations.