High-precision calculation of the strange nucleon electromagnetic form factors

Abstract

We report a direct lattice QCD calculation of the strange nucleon electromagnetic form factors G[s over E] and G[s over M] in the kinematic range 0 ≤ Q[superscript 2] ≲ 1.2 GeV[superscript 2]. For the first time, both G[s over E] and G[s over M] 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.