High-precision calculation of the strange nucleon electromagnetic form factors

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 $0\ensuremath{\le}{Q}^{2}\ensuremath{\lesssim}1.2\text{ }\text{ }{\mathrm{GeV}}^{2}$. 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.