Analyses of pion-nucleon elastic scattering amplitudes up to O(p(4)) in the extended-on-mass-shell subtraction scheme

We extend the analysis of elastic pion-nucleon scattering up to O(p(4)) level using the extended-on-mass-shell subtraction scheme within the framework of covariant baryon chiral perturbation theory. Numerical fits to partial wave phase shift data up to root s = 1.13 GeV are performed to pin down the free low energy constants. A good description of the existing phase shift data is achieved. We find a good convergence for the chiral series at O(p(4)), considerably improved with respect to the O(p(3))-level analyses found in previous literature. Also, the leading order contribution from explicit Delta(1232) resonance and partially-included Delta(1232) loop contribution are included to describe the phase shift data up to root s = 1.20 GeV. As phenomenological applications, we investigate chiral corrections to the Goldberger-Treiman relation and find that it converges rapidly, and the O(p(3)) correction is found to be very small: similar or equal to 0.2%. We also get a reasonable prediction of the pion-nucleon sigma term sigma(pi N) up to O(p(4)) by performing fits including both the pion-nucleon partial wave phase shift data and the lattice QCD data. We report that sigma(pi N) = 52 +/- 7 MeV from the fit without Delta(1232), and sigma(pi N) = 45 +/- 6 MeV from the fit with explicit Delta(1232). DOI: 10.1103/PhysRevD.87.054019http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000316389600002&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Astronomy & AstrophysicsPhysics, Particles & FieldsSCI(E)19ARTICLE5null8