The strange and light quark contributions to the nucleon mass from Lattice QCD

TL;DR

This study uses lattice QCD to quantify the contributions of strange and light quarks to the nucleon mass, providing new insights into nucleon structure and quark mass effects.

Contribution

It presents the first lattice QCD calculation of the strangeness and light quark fractions of the nucleon mass with non-perturbative renormalization and extrapolation to physical quark masses.

Findings

The pion-nucleon sigma-term is estimated at 38(12) MeV.

The strangeness contribution to the nucleon mass is very small, at 0.012(14).

Results are obtained using n_F=2 sea quarks with a pion mass of about 285 MeV.

Abstract

We determine the strangeness and light quark fractions of the nucleon mass by computing the quark line connected and disconnected contributions to the matrix elements m_q <N|qbar q|N> in lattice QCD, using the non-perturbatively improved Sheikholeslami-Wohlert Wilson Fermionic action. We simulate n_F=2 mass degenerate sea quarks with a pion mass of about 285 MeV and a lattice spacing a approx 0.073 fm. The renormalization of the matrix elements involves mixing between contributions from different quark flavours. The pion-nucleon sigma-term is extrapolated to physical quark masses exploiting the sea quark mass dependence of the nucleon mass. We obtain the renormalized values \sigma_{\pi N} = 38(12) MeV at the physical point and f_{T_s}=\sigma_s/m_N= 0.012(14)^{+10}_{-3} for the strangeness contribution at our larger than physical sea quark mass.