We report a lattice QCD calculation of the strange quark contribution to the nucleon’s magnetic moment and charge radius. This analysis presents the first direct determination of strange electromagnetic form factors including at the physical pion mass. We perform a model-independent extraction of the strange magnetic moment and the strange charge radius from the electromagnetic form factors in the momentum transfer range of 0.051 GeV2 ≲ Q2 ≲ 1.31 GeV2. The finite lattice spacing and finite volume corrections are included in a global fit with 24 valence quark masses on four lattices with different lattice spacings, different volumes, and four sea quark masses including one at the physical pion mass. We obtain the strange magnetic moment GsM(0) = −0.064(14)(09)μN. The four-sigma precision in statistics is achieved partly due to low-mode averaging of the quark loop and low-mode substitution to improve the statistics of the nucleon propagator. We also obtain the strange charge radius ⟨r2s⟩E = −0.0043(16)(14) fm2.
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This work is supported in part by the U.S. DOE Grant No. DE-SC0013065. This research used resources of the Oak Ridge Leadership Computing Facility at the Oak Ridge National Laboratory, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC05-00OR22725. A. A. is supported by the NSF CAREER Grant No. PHY-1151648 and in part by the DOE Grant No. DE-FG02-95ER-40907.
Sufian, Raza Sabbir; Yang, Yi-Bo; Alexandru, Andrei; Draper, Terrence; Liang, Jian; and Liu, Keh-Fei, "Strange Quark Magnetic Moment of the Nucleon at the Physical Point" (2017). Physics and Astronomy Faculty Publications. 514.