Abstract
Lattice calculations of the proton spin components is reviewed. The lattice results of the quark spin from the axial-vector current matrix element at ∼ 0.3−0.4 is smaller than those from the constituent quark models. This is largely due to the fact that the vacuum polarization contribution from the disconnected insertion is negative. Its connection with the anomalous Ward identity is clarified and verified numerically. This resolves the contentious issue in the “proton spin crisis.” The glue spin and angular momentum are found to be large and there is notable contribution from the quark orbital angular momentum. Renormalization, mixing, and normalization of the quark and glue angular momenta are discussed. With sufficient precision, they can be compared with more precise experimental measurements when the electron-ion collider facility is available.
| Original language | English |
|---|---|
| Article number | 8 |
| Journal | AAPPS Bulletin |
| Volume | 32 |
| Issue number | 1 |
| DOIs | |
| State | Published - Dec 2022 |
Bibliographical note
Publisher Copyright:© 2022, The Author(s).
Funding
The author is indebted to M. Engelhardt, X. Ji, C. Lorc\u00E9, Yi-Bo Yang, F. Yuan, and Y. Zhao for fruitful discussions. He also thanks Jian Liang, G. Wang, and Yi-Bo Yang for the results of the \u03C7 QCD Collaboration. This work is partially support by the U.S. DOE grant DE-SC0013065 and DOE Grant No. DE-AC05-06OR23177 which is within the framework of the TMD Topical Collaboration. 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 used Stampede and Frontera time under the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by National Science Foundation Grant No. ACI-1053575. We also thank the National Energy Research Scientific Computing Center (NERSC) for providing HPC resources that have contributed to the research results reported within this paper. We also acknowledge the facilities of the USQCD Collaboration used for this research in part, which are funded by the Office of Science of the U.S. Department of Energy.
| Funders | Funder number |
|---|---|
| National Energy Research Scientific Computing Center | |
| National Science Foundation Office of International Science and Engineering | |
| U.S. Department of Energy Chinese Academy of Sciences Guangzhou Municipal Science and Technology Project Oak Ridge National Laboratory Extreme Science and Engineering Discovery Environment National Science Foundation National Energy Research Scientific Computing Center National Natural Science Foundation of China | ACI-1053575 |
| U.S. Department of Energy Oak Ridge National Laboratory U.S. Department of Energy National Science Foundation National Energy Research Scientific Computing Center | DE-AC05-00OR22725, DE-SC0013065, DE-AC05-06OR23177 |
Keywords
- Gluon spin
- Lattice QCD
- Quantum chromodynamics
- Quark spin
ASJC Scopus subject areas
- General Physics and Astronomy