Sigma terms from an SU(3) chiral extrapolation

TL;DR

This paper presents a precise lattice QCD analysis of octet baryon masses, leading to improved estimates of the pion-nucleon and strangeness sigma terms using chiral extrapolation and the Feynman-Hellmann relation.

Contribution

It introduces a controlled chiral extrapolation method for lattice data that yields more accurate sigma term determinations with reduced model dependence.

Findings

Pion-nucleon sigma term: 45 ± 6 MeV

Strangeness sigma term: 21 ± 6 MeV

Results agree with experimental and other lattice data

Abstract

We report a new analysis of lattice simulation results for octet baryon masses in 2+1-flavor QCD, with an emphasis on a precise determination of the strangeness nucleon sigma term. A controlled chiral extrapolation of a recent PACS-CS Collaboration data set yields baryon masses which exhibit remarkable agreement both with experimental values at the physical point and with the results of independent lattice QCD simulations at unphysical meson masses. Using the Feynman-Hellmann relation, we evaluate sigma commutators for all octet baryons. The small statistical uncertainty, and considerably smaller model-dependence, allows a signifcantly more precise determination of the pion-nucleon sigma commutator and the strangeness sigma term than hitherto possible, namely {\sigma}{\pi}N=45 \pm 6 MeV and {\sigma}s = 21 \pm 6 MeV at the physical point.