High-precision calculation of the strange nucleon electromagnetic form factors

TL;DR

This paper presents a high-precision lattice QCD calculation of strange nucleon electromagnetic form factors, demonstrating both are nonzero and providing detailed shape and radius measurements with unprecedented accuracy.

Contribution

It is the first to show both $G_E^s$ and $G_M^s$ are nonzero with high significance using near-physical lattice parameters and advanced variance reduction techniques.

Findings

Both $G_E^s$ and $G_M^s$ are nonzero with high significance

Determined strange electric and magnetic radii and magnetic moment

Results agree with parity-violating electron-proton scattering data

Abstract

We report a direct lattice QCD calculation of the strange nucleon electromagnetic form factors $G_E^s$ and $G_M^s$ in the kinematic range $0 \leq Q^2 \lesssim 1.2\: {\rm GeV}^2$. For the first time, both $G_E^s$ and $G_M^s$ are shown to be nonzero with high significance. This work uses closer-to-physical lattice parameters than previous calculations, and achieves an unprecedented statistical precision by implementing a recently proposed variance reduction technique called hierarchical probing. We perform model-independent fits of the form factor shapes using the $z$-expansion and determine the strange electric and magnetic radii and magnetic moment. We compare our results to parity-violating electron-proton scattering data and to other theoretical studies.