We present a calculation of the strange and charm quark contributions to the nucleon spin from the anomalous Ward identity (AWI). This is performed with overlap valence quarks on 2 + 1-flavor domain-wall fermion gauge configurations on a 243 × 64 lattice with lattice spacing a−1 = 1.73 GeV and the light sea mass at mπ = 330 MeV. To satisfy the AWI, the overlap fermion for the pseudoscalar density and the overlap Dirac operator for the topological density, which do not have multiplicative renormalization, are used to normalize the form factor of the local axial-vector current at finite q2. For the charm quark, we find that the negative pseudoscalar term almost cancels the positive topological term. For the strange quark, the pseudoscalar term is less negative than that of the charm. By imposing the AWI, the strange gA(q2) at q2=0 is obtained by a global fit of the pseudoscalar and the topological form factors, together with gA(q2) and the induced pseudoscalar form factor hA(q2) at finite q2. The chiral extrapolation to the physical pion mass gives Δs + Δ¯s = −0.0403(44)(78).
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This work is supported in part by the National Science Foundation of China (NSFC) under Project No. 11405178, the Youth Innovation Promotion Association of CAS (2015013), and the U.S. DOE Grant No. DE-SC0013065. A. A. is supported in part by the National Science Foundation CAREER Grant No. PHY-1151648 and by U.S. DOE Grant No. DE-FG02-95ER40907. 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. This work also used the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by National Science Foundation Grant No. ACI-1053575.
Gong, Ming; Yang, Yi-Bo; Liang, Jian; Alexandru, Andrei; Draper, Terrence; and Liu, Keh-Fei, "Strange and Charm Quark Spins from the Anomalous Ward Identity" (2017). Physics and Astronomy Faculty Publications. 515.