Recent Advances in Transverse-Momentum–Dependent Distributions in Lattice QCD

Abstract

Unraveling the three-dimensional structure of hadrons is a central objective in modern nuclear and particle physics. Transverse Momentum Dependent parton distributions (TMDs) provide crucial insights into the interplay between partonic transverse motion and spin, and are indispensable for describing a wide range of high-energy processes at facilities such as JLab, COMPASS, the LHC, and the upcoming Electron-Ion Collider. In recent years, significant progress has been made in accessing TMDs from lattice QCD using novel approaches. Methods based on ratios of Mellin moments, large-momentum effective theory (LaMET), and Coulomb-gauge techniques have enabled first-principles investigations of the Collins-Soper kernel, intrinsic soft functions, TMD wave functions, and TMDPDFs. Recent lattice results for both unpolarized and spin-dependent distributions, including the Boer-Mulders function, demonstrate the feasibility of extracting transverse-momentum–dependent information directly from QCD. This paper reviews recent advances in lattice-QCD studies of TMDs, outlines remaining challenges such as continuum and infinite-momentum extrapolations, and discusses future directions toward precision determinations of hadron structure in three dimensions.