Total Gluon Helicity Contribution to the Proton Spin from Lattice QCD
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arXiv
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| Auteurs principaux: | , , , , , , , , , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866912827102461952 |
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| author | Zhao, Dian-Jun Chen, Long Dong, Hongxin Ji, Xiangdong Liu, Liuming Pang, Zhuoyi Schäfer, Andreas Sun, Peng Yang, Yi-Bo Zhang, Jian-Hui Zhong, Shiyi |
| author_facet | Zhao, Dian-Jun Chen, Long Dong, Hongxin Ji, Xiangdong Liu, Liuming Pang, Zhuoyi Schäfer, Andreas Sun, Peng Yang, Yi-Bo Zhang, Jian-Hui Zhong, Shiyi |
| contents | We report a state-of-the-art lattice QCD calculation of the total gluon helicity contribution to the proton spin, $ΔG$. The calculation is done on ensembles with three different lattice spacings $a=\{0.08, 0.09, 0.11\}$ fm. By employing distillation and momentum smearing for proton external states, we extract the bare matrix elements of the topological current $K^μ$ using 5-HYP smeared Coulomb gauge fixing configurations. Furthermore, we apply a non-perturbative $\mathrm{RI/MOM}$ renormalization scheme augmented by the Cluster Decomposition Error Reduction (CDER) technique to determine the renormalization constants of $K^μ$. The results obtained from different components $K^{t,i}$ (with $i$ being the direction of proton momentum or polarization) are consistent with Lorentz covariance within uncertainties. After extrapolating to the continuum limit, $ΔG$ is found to be $ΔG = 0.231(17)^{\mathrm{sta.}}(44)^{\mathrm{sym.}}$ at the $\overline{\mathrm{MS}}$ scale $μ^2=10\ \mathrm{GeV}^2$, which constitutes approximately $46(9)\%$ of the proton spin. |
| format | Preprint |
| id |
arxiv_https___arxiv_org_abs_2512_24315 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Total Gluon Helicity Contribution to the Proton Spin from Lattice QCD Zhao, Dian-Jun Chen, Long Dong, Hongxin Ji, Xiangdong Liu, Liuming Pang, Zhuoyi Schäfer, Andreas Sun, Peng Yang, Yi-Bo Zhang, Jian-Hui Zhong, Shiyi High Energy Physics - Lattice High Energy Physics - Phenomenology High Energy Physics - Theory Nuclear Experiment Nuclear Theory We report a state-of-the-art lattice QCD calculation of the total gluon helicity contribution to the proton spin, $ΔG$. The calculation is done on ensembles with three different lattice spacings $a=\{0.08, 0.09, 0.11\}$ fm. By employing distillation and momentum smearing for proton external states, we extract the bare matrix elements of the topological current $K^μ$ using 5-HYP smeared Coulomb gauge fixing configurations. Furthermore, we apply a non-perturbative $\mathrm{RI/MOM}$ renormalization scheme augmented by the Cluster Decomposition Error Reduction (CDER) technique to determine the renormalization constants of $K^μ$. The results obtained from different components $K^{t,i}$ (with $i$ being the direction of proton momentum or polarization) are consistent with Lorentz covariance within uncertainties. After extrapolating to the continuum limit, $ΔG$ is found to be $ΔG = 0.231(17)^{\mathrm{sta.}}(44)^{\mathrm{sym.}}$ at the $\overline{\mathrm{MS}}$ scale $μ^2=10\ \mathrm{GeV}^2$, which constitutes approximately $46(9)\%$ of the proton spin. |
| title | Total Gluon Helicity Contribution to the Proton Spin from Lattice QCD |
| topic | High Energy Physics - Lattice High Energy Physics - Phenomenology High Energy Physics - Theory Nuclear Experiment Nuclear Theory |
| url | https://arxiv.org/abs/2512.24315 |