Nucleon strange electromagnetic form factors

TL;DR

This study uses advanced lattice QCD simulations to accurately determine the strange electromagnetic form factors of the nucleon, revealing non-zero contributions from strange quarks to the proton's electromagnetic structure.

Contribution

First lattice QCD calculation including all sea quarks at physical masses to determine nucleon strange form factors up to 0.8 GeV$^2$.

Findings

Strange electric and magnetic form factors are statistically non-zero.

Strange magnetic moment is -0.017(4).

Strange charge radius is -0.0048(6) fm$^2$.

Abstract

The role of the strange quarks on the low-energy interactions of the proton can be probed through the strange electromagnetic form factors. Knowledge of these form factors provides essential input for parity-violating processes and contributes to the understanding of the sea quark dynamics. We determine the strange electromagnetic form factors of the nucleon within the lattice formulation of Quantum Chromodynamics using simulations that include light, strange and charm quarks in the sea all tuned to their physical mass values. We employ state-of-the-art techniques to accurately extract the form factors for values of the momentum transfer square up to 0.8~GeV$^2$. We find that both the electric and magnetic form factors are statistically non-zero. We obtain for the strange magnetic moment $\mu^s=-0.017(4)$, the strange magnetic radius $\langle r^2_M \rangle^s=-0.015(9)$~fm$^2$, and the strange charge radius $\langle r^2_E \rangle^s=-0.0048(6)$~fm$^2$.