Title: Total Gluon Helicity Contribution to the Proton Spin from Lattice QCD
Date: Jun 9, 2026
Time: 14:00 - 15:00
Speaker: Dr. Dian-Jun
Affiliation: The Chinese University of Hongkong, Shenzen
Abstract: We report a state-of-the-art lattice QCD calculation of the total gluon helicity contribution to the proton spin, $\Delta G$. 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 $K_\mu$ using 5-HYP smeared Coulomb gauge fixing configurations.
Furthermore, we apply a non-perturbative RI/MOM renormalization scheme augmented by the Cluster Decomposition Error Reduction (CDER) technique to determine the renormalization constants of $K_\mu$ .
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, $\Delta G$ is found to be $\Delta G = 0.231(17)^{\mathrm{sta.}} (44)^{\mathrm{sym.}} at the $\overline{\mathrm{MS}}$ scale $\mu^2 = 10\ \mathrm{GeV}^2$ , which constitutes approximately $46(9)\%$ of the proton spin.