Nucleon mass and sigma term from lattice QCD with two light fermion flavors

TL;DR

This study uses lattice QCD data with two light fermion flavors to analyze the nucleon mass and sigma term, fitting the data with covariant baryon chiral perturbation theory to extract physical parameters.

Contribution

It introduces a simultaneous fit of nucleon mass data and the pion-nucleon sigma-term using covariant baryon chiral perturbation theory, extending analysis to lower pion masses.

Findings

Nucleon mass data well described by O(p^4) BChPT below 435 MeV

Sigma-term at physical point estimated as 37(8)(6) MeV

Determined Sommer parameter r_0=0.501(10)(11) fm

Abstract

We analyze Nf=2 nucleon mass data with respect to their dependence on the pion mass down to mpi = 157 MeV and compare it with predictions from covariant baryon chiral perturbation theory (BChPT). A novel feature of our approach is that we fit the nucleon mass data simultaneously with the directly obtained pion-nucleon sigma-term. Our lattice data below mpi = 435 MeV is well described by O(p^4) BChPT and we find sigma=37(8)(6) MeV for the sigma-term at the physical point. Using the nucleon mass to set the scale we obtain a Sommer parameter of r_0=0.501(10)(11) fm.