$\pi$N and strangeness sigma terms at the physical point with chiral fermions

TL;DR

This study uses lattice QCD with chiral fermions to accurately compute the pion-nucleon and strangeness sigma terms, including chiral, continuum, and volume corrections, providing precise scalar matrix elements for light and strange quarks.

Contribution

It presents the first lattice QCD calculations of $\sigma_{\pi N}$ and $\sigma_{sN}$ with chiral fermions, including comprehensive corrections and excited-state subtraction.

Findings

$\sigma_{\pi N}=45.9(7.4)(2.8)$ MeV, with 20% from disconnected insertions.

$\sigma_{sN}=40.2(11.7)(3.5)$ MeV, smaller than $\sigma_{\pi N}$.

Strangeness to light scalar matrix element ratio $y=0.09(3)(1)$.

Abstract

Lattice QCD calculations with chiral fermions of the $\pi$N sigma term $\sigma_{\pi N}$ and strangeness sigma term $\sigma_{sN}$ including chiral interpolation with continuum and volume corrections are provided in this work, with the excited-state contaminations subtracted properly. We calculate the scalar matrix element for the light/strange quark directly and find $\sigma_{\pi N}=45.9(7.4)(2.8)$ MeV, with the disconnected insertion part contributing 20(12)(4)\%, and $\sigma_{sN}=40.2(11.7)(3.5)$ MeV, which is somewhat smaller than $\sigma_{\pi N}$. The ratio of the strange/light scalar matrix elements is $y$ = 0.09(3)(1).