Nucleon mass and pion-nucleon sigma term from a chiral analysis of lattice QCD world data

The chiral behavior of the nucleon mass is studied within the covariant SU(2) baryon chiral perturbation theory up to order p(4). Lattice QCD data for the ensembles of 2 and 2 + 1 flavors are separately fitted, paying special attention to explicit Delta(1232) degrees of freedom, finite volume corrections and finite spacing effects. In the case of the 2 flavor ensemble, we fit simultaneously nucleon mass data together with new and updated data for the sigma(pi N) term both in their dimensionless forms and determine a Sommer-scale of r(0) = 0.493(23) fm. We obtain low-energy constants of natural size that are compatible with the rather linear pion-mass dependence observed in lattice QCD and report a preliminary updated value of sigma(pi N) = 43(5)(4) MeV for the 2 flavor case and sigma(pi N) = 52(3)(8) MeV for 2 + 1 flavor case.