AI and the World's Hard Problems · Physics · arXiv · 2026-10-22
Mellin Moments of Proton Unpolarized GPDs at Nonzero Skewness from Lattice QCD with a Neural-Network Parametrization
Lattice QCD is used to determine the generalized form factors entering the first four Mellin moments of the unpolarized isovector u-d proton GPDs at nonzero skewness. Each form factor is parameterized by an artificial neural network as a continuous function of the invariant momentum transfer squared, and fitting to the lattice-extracted reduced Ioffe-time distributions determines fourteen form factors, including the skewness-dependent ones. The extracted form factors give a quark total angular momentum of the isovector combination, J^{u-d}=0.296(11)(7) in the MSbar scheme at mu=2 GeV, consistent with previous lattice determinations but with smaller total uncertainty, and impact-parameter distributions of the first three moments are also obtained.