Exploring strange nucleon form factors on the lattice

TL;DR

This paper explores techniques for calculating strange nucleon form factors on the lattice, providing initial results that suggest small or negligible strange electric and magnetic form factors and a notable scalar matrix element.

Contribution

It introduces methods for evaluating sea quark contributions to nucleon form factors on the lattice and applies them to compute strange form factors with preliminary findings.

Findings

Strange electric and magnetic form factors are small and consistent with zero.

The strange scalar matrix element shows a strong signal.

Results favor a small negative strange axial form factor.

Abstract

We discuss techniques for evaluating sea quark contributions to hadronic form factors on the lattice and apply these to an exploratory calculation of the strange electromagnetic, axial, and scalar form factors of the nucleon. We employ the Wilson gauge and fermion actions on an anisotropic 24^3 x 64 lattice, probing a range of momentum transfer with Q^2 < 1 GeV^2. The strange electric and magnetic form factors, G_E^s(Q^2) and G_M^s(Q^2), are found to be small and consistent with zero within the statistics of our calculation. The lattice data favor a small negative value for the strange axial form factor G_A^s(Q^2) and exhibit a strong signal for the bare strange scalar matrix element <N|ss|N>_0. We discuss the unique systematic uncertainties affecting the latter quantity relative to the continuum, as well as prospects for improving future determinations with Wilson-like fermions.