Strange and charm quark spins from the anomalous Ward identity

Journal Article · Thu Jun 22 00:00:00 EDT 2017 · Physical Review D

DOI:https://doi.org/10.1103/PhysRevD.95.114509· OSTI ID:1599053

Gong, Ming  ^[1]; Yang, Yi-Bo  ^[2]; Liang, Jian ^[2]; Alexandru, Andrei  ^[3]; Draper, Terrence ^[2]; Liu, Keh-Fei  ^[2]

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1. Chinese Academy of Sciences (CAS), Beijing (China). Inst. of High Energy Physics
2. University of Kentucky, Lexington, KY (United States)
3. The George Washington University, Washington, DC (United States)

In this article, 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 $24^3\times 64$ lattice with lattice spacing $a^{-1}=1.73\mathrm{GeV}$ and the light sea mass at $m_{\pi }=330\mathrm{MeV}$. 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 $q^2$. 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 $g_A\left(q^2\right)$ at $q^2=0$ is obtained by a global fit of the pseudoscalar and the topological form factors, together with $g_A\left(q^2\right)$ and the induced pseudoscalar form factor $h_A\left(q^2\right)$ at finite $q^2$. The chiral extrapolation to the physical pion mass gives $\mathrm{\Delta }s+\mathrm{\Delta }\overline{s}=-0.0403\left(44\right)\left(78\right)$.

• Research Organization: Univ. of Kentucky, Lexington, KY (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Nuclear Physics (NP); National Science Foundation of China (NSFC); National Science Foundation (NSF)
• Contributing Organization: χQCD Collaboration
• Grant/Contract Number: SC0013065; FG02-95ER40907; AC05-00OR22725; 11405178; PHY-1151648; ACI-1053575
• OSTI ID: 1599053
• Alternate ID(s): OSTI ID: 1365604
• Report Number(s): DOE-UKY-13065-1511.03671; PRVDAQ; arXiv:1511.03671; TRN: US2103418
• Journal Information: Physical Review D, Vol. 95, Issue 11; ISSN 2470-0010
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English

Related Subjects

73 NUCLEAR PHYSICS AND RADIATION PHYSICS
72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
Lattice QCD
Charm quark
Strange quark
Flavor symmetries