Speaker
Description
A class of transverse momentum-dependent (TMD) proton observables that can be evaluated within Lattice QCD in a particularly robust fashion are ratios of TMD Mellin moments. These observables are thus particularly well-suited for achieving a controlled, quantitative connection to phenomenology. Lattice QCD studies of such TMD ratios are presented, based on calculations of proton matrix elements of quark bilocal operators, including an appropriate gauge connection between the quarks. Several challenges faced by such calculations are addressed, and results are shown for the Sivers, $g_{1T}$ worm gear, and $h_{1L}^{\perp } $ worm gear transverse momentum shifts. A striking prediction for the relationship between the latter two observables emerges.