Strange Quark Magnetic Moment of the Nucleon at the Physical Point

• Published in: Physical review letters 2017-01, Vol.118 (4), p.042001-042001, Article 042001
• Main Authors: Sufian, Raza Sabbir, Yang, Yi-Bo, Alexandru, Andrei, Draper, Terrence, Liang, Jian, Liu, Keh-Fei
• Format: Article
• Language: English
• Subjects: Lattices; Magnetic moment; Mathematical analysis; Mathematical models; Nucleons; Quarks; Statistics; Texts
• ISSN: 0031-9007; 1079-7114
• DOI: 10.1103/PhysRevLett.118.042001

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  GeV^{2}≲Q^{2}≲1.31  GeV^{2}. 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 G_{M}^{s}(0)=-0.064(14)(09)μ_{N}. 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 ⟨r_{s}^{2}⟩_{E}=-0.0043(16)(14)  fm^{2}.