We report the first lattice QCD calculation of the glue spin in the nucleon. The lattice calculation is carried out with valence overlap fermions on 2 + 1 flavor domain-wall fermion gauge configurations on four lattice spacings and four volumes including an ensemble with physical values for the quark masses. The glue spin SG in the Coulomb gauge in the modified minimal subtraction (MS¯) scheme is obtained with one-loop perturbative matching. We find the results fairly insensitive to lattice spacing and quark masses. We also find that the proton momentum dependence of SG in the range 0 ≤ |p→|< 1.5 GeV is very mild, and we determine it in the large-momentum limit to be SG = 0.251(47)(16) at the physical pion mass in the MS¯ scheme at μ2 = 10 GeV2. If the matching procedure in large-momentum effective theory is neglected, SG is equal to the glue helicity measured in high-energy scattering experiments.
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This work is supported in part by 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. Y. Z. is supported in part by the U.S. Department of Energy Office of Science, Office of Nuclear Physics under Awards No. DE-FG02-93ER-40762 and No. DE-AC02-05CH11231. 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.
See Supplemental Material at http://link.aps.org/supplemental/10.1103/PhysRevLett.118.102001 for the details of the numerical simulation setup and the two-state fits used to obtain the glue spin matrix element.
Yang, Yi-Bo; Sufian, Raza Sabbir; Alexandru, Andrei; Draper, Terrence; Glatzmaier, Michael J.; Liu, Keh-Fei; and Zhao, Yong, "Glue Spin and Helicity in the Proton from Lattice QCD" (2017). Physics and Astronomy Faculty Publications. 540.