Nucleon strange quark content from two-flavor lattice QCD with exact chiral symmetry

Abstract

The strange quark content of the nucleon $⟨N|\overline{s}s|N⟩$ is calculated in dynamical lattice QCD employing the overlap fermion formulation. For this quantity, exact chiral symmetry guaranteed by the Ginsparg-Wilson relation is crucial to avoid large contamination due to a possible operator mixing with $\overline{u}u+\overline{d}d$. Gauge configurations are generated with two dynamical flavors on a ${16}^{3}\ifmmode\times\else\texttimes\fi{}32$ lattice at a lattice spacing $a\ensuremath{\simeq}0.12\text{ }\text{ }\mathrm{fm}$. We directly calculate the relevant three-point function on the lattice including a disconnected strange quark loop utilizing the techniques of the all-to-all quark propagator and low-mode averaging. Our result ${f}_{{T}_{s}}={m}_{s}⟨N|\overline{s}s|N⟩/{M}_{N}=0.032(8{)}_{\mathrm{stat}}(22{)}_{\mathrm{sys}}$, where ${m}_{s}$ and ${M}_{N}$ are strange quark and nucleon masses, is in good agreement with our previous indirect estimate using the Feynman-Hellmann theorem.