TY - JOUR
T1 - Quark spin in proton from anomalous Ward indentity
AU - Yang, Yi Bo
AU - Gong, Ming
AU - Liu, Keh Fei
AU - Sun, Mingyang
N1 - Publisher Copyright:
© Copyright owned by the author(s) under the terms of the Creative Commons Attribution-NonCommercial-ShareAlike Licence.
Copyright:
Copyright 2018 Elsevier B.V., All rights reserved.
PY - 2014
Y1 - 2014
N2 - We report a quark spin calculation from the anomalous Ward identity with overlap fermions on 2+1 flavor dynamical fermion configurations with light sea quark masses. Such a formulation decomposes the divergence of the flavor-singlet axial-vector current into a quark pseudoscalar term and a triangle anomaly term, flavor by flavor. A large negative contribution from the anomaly term is observed and it is canceled within errors by the contribution from the pseudoscalar term in the disconnected insertion in the heavy quark region. On the other hand, net negative contributions are obtained for the light and strange quarks in the disconnected insertion, since their quark pseudoscalar terms are smaller than that of the heavy quark. Our results are obtained from the 2+1 flavor domain wall fermion configurations on the 243 ×64 lattice with a-1 = 1.78(5) GeV and the light sea quark at mπ = 330 MeV. We use the overlap fermion for the valence and the quark loop so that the renormalization constants Zm and Zp cancel in the pseudoscalar operator 2mP. In addition, the overlap Dirac operator is used to calculate the local topological charge in the anomaly so that there is no renormalization for the anomaly term either. In this study, we find the total quark spin to be small mainlyly due to the large negative anomaly term which could be the source for the 'proton spin crisis'.
AB - We report a quark spin calculation from the anomalous Ward identity with overlap fermions on 2+1 flavor dynamical fermion configurations with light sea quark masses. Such a formulation decomposes the divergence of the flavor-singlet axial-vector current into a quark pseudoscalar term and a triangle anomaly term, flavor by flavor. A large negative contribution from the anomaly term is observed and it is canceled within errors by the contribution from the pseudoscalar term in the disconnected insertion in the heavy quark region. On the other hand, net negative contributions are obtained for the light and strange quarks in the disconnected insertion, since their quark pseudoscalar terms are smaller than that of the heavy quark. Our results are obtained from the 2+1 flavor domain wall fermion configurations on the 243 ×64 lattice with a-1 = 1.78(5) GeV and the light sea quark at mπ = 330 MeV. We use the overlap fermion for the valence and the quark loop so that the renormalization constants Zm and Zp cancel in the pseudoscalar operator 2mP. In addition, the overlap Dirac operator is used to calculate the local topological charge in the anomaly so that there is no renormalization for the anomaly term either. In this study, we find the total quark spin to be small mainlyly due to the large negative anomaly term which could be the source for the 'proton spin crisis'.
UR - http://www.scopus.com/inward/record.url?scp=85014733846&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85014733846&partnerID=8YFLogxK
M3 - Conference article
AN - SCOPUS:85014733846
VL - Part F130500
M1 - 138
Y2 - 23 June 2014 through 28 June 2014
ER -