Nucleon sigma term and strange quark content from lattice QCD with exact chiral symmetry

TL;DR

This study uses lattice QCD with exact chiral symmetry to accurately compute the nucleon sigma term and strange quark content, revealing smaller values than previous estimates and enhancing understanding of nucleon structure.

Contribution

It introduces a lattice QCD calculation with overlap fermions to precisely determine the nucleon sigma term and strange quark content, improving upon prior estimates.

Findings

Strange quark content is significantly smaller than previous lattice and phenomenological results.

Utilizes overlap fermions to preserve chiral symmetry on the lattice.

Analyzes nucleon mass with baryon chiral perturbation theory to extract quark contributions.

Abstract

We calculate the nucleon sigma term in two-flavor lattice QCD utilizing the Feynman-Hellman theorem. Both sea and valence quarks are described by the overlap fermion formulation, which preserves exact chiral and flavor symmetries on the lattice. We analyse the lattice data for the nucleon mass using the analytical formulae derived from the baryon chiral perturbation theory. From the data at valence quark mass set different from sea quark mass, we may extract the sea quark contribution to the sigma term, which corresponds to the strange quark content. We find that the strange quark content is much smaller than the previous lattice calculations and phenomenological estimates.