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 super(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] sub([pi])N term both in their dimensionless forms and determine a Sommer-scale of r sub(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] sub([pi])N = 43(5)(4) MeV for the 2 flavor case and [sigma] sub([pi])N = 52(3)(8) MeV for 2 + 1 flavor case.