Nucleon mass, sigma term and lattice QCD

TL;DR

This paper uses relativistic baryon chiral perturbation theory to analyze lattice QCD data, accurately interpolating the nucleon mass dependence on quark mass and determining key physical parameters like the sigma term.

Contribution

It provides a precise interpolation method for nucleon mass from lattice QCD data using chiral perturbation theory up to order p^4, with minimal uncertainties.

Findings

Nucleon mass in the chiral limit M_0 ≈ 0.88 GeV

Pion-nucleon sigma term σ_N ≈ 49 MeV

Good fit achieved at one-loop level p^3 order

Abstract

We investigate the quark mass dependence of the nucleon mass M_N. An interpolation of this observable, between a selected set of fully dynamical two-flavor lattice QCD data and its physical value, is studied using relativistic baryon chiral perturbation theory up to order p^4. In order to minimize uncertainties due to lattice discretization and finite volume effects our numerical analysis takes into account only simulations performed with lattice spacings a<0.15 fm and m_pi L>5. We have also restricted ourselves to data with m_pi<600 MeV and m_sea=m_val. A good interpolation function is found already at one-loop level and chiral order p^3. We show that the next-to-leading one-loop corrections are small. From the p^4 numerical analysis we deduce the nucleon mass in the chiral limit, M_0 approx 0.88 GeV, and the pion-nucleon sigma term sigma_N= (49 +/- 3) MeV at the physical value of the pion mass.