Strange and Charm Quark Spins from the Anomalous Ward Identity

Authors

Ming Gong, Chinese Academy of Science, China
Yi-Bo Yang, University of KentuckyFollow
Jian Liang, University of KentuckyFollow
Andrei Alexandru, The George Washington University
Terrence Draper, University of KentuckyFollow
Keh-Fei Liu, University of KentuckyFollow

Abstract

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 m_π = 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 g_A(q²) at q²=0 is obtained by a global fit of the pseudoscalar and the topological form factors, together with g_A(q²) and the induced pseudoscalar form factor h_A(q²) at finite q². The chiral extrapolation to the physical pion mass gives Δs + Δ¯s = −0.0403(44)(78).

Document Type

Article

Publication Date

6-22-2017

Notes/Citation Information

Published in Physical Review D, v. 95, issue 11, 114509, p. 1-9.

© 2017 American Physical Society

The copyright holder has granted permission for posting the article here.

This group of authors is collectively known as the χQCD Collaboration.

Digital Object Identifier (DOI)

https://doi.org/10.1103/PhysRevD.95.114509

Funding Information

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.

Repository Citation

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.
https://uknowledge.uky.edu/physastron_facpub/515