Gómez Nicola, ÁngelNieves, J.Peláez Sagredo, José RamónRuiz Arriola, E.2023-06-202023-06-202000-07-270370-269310.1016/S0370-2693(00)00761-9https://hdl.handle.net/20.500.14352/59585© 2000 Elsevier Science B.V. All rights reserved. This research was supported by DGES under contract PB98-1367 and by the Junta de Andalucía. Work partially supported by DGICYT under contracts AEN97-1693 and PB98-0782. We thank P. Buttiker, J.A.Oller and E.Oset for useful comments and discussions.We show how the unitarized description of pion nucleon scattering within Heavy Baryon Chiral Perturbation Theory can be considerably improved, by a suitable reordering of the expansion over the nucleon mass. Within this framework, the ∆ resonance and its associated pole can be recovered from the chiral parameters obtained from low-energy determinations. In addition, we can obtain a good description of the six S and P wave phase shifts in terms of chiral parameters with a natural size and compatible with the Resonance Saturation Hypothesis.engjournal articlehttp://dx.doi.org/10.1016/S0370-2693(00)00761-9http://www.sciencedirect.comopen access51-73Nucleon scatteringElastic-scatteringMeson interactionsOne-loopApproximationAmplitudeModelFísica-Modelos matemáticosFísica matemática