Process-dependent transverse momentum distributions from lattice QCD

Abstract

Certain single-spin asymmetries in semi-inclusive DIS (SIDIS) and the Drell-Yan process (DY) can be explained by transverse momentum dependent parton distribution functions (TMDs) that are predicted to differ in sign for SIDIS and DY. On the lattice, we can use non-local operators with U-shaped Wilson lines to study these TMDs, in particular the Sivers- and the Boer-Mulders function. We discuss the method, its limitations and preliminary results from an exploratory calculation using lattices generated by the MILC and LHP collaborations.