Transverse Momentum Distributions of Quarks in the Nucleon from Lattice QCD

Bernhard Musch 
JLab

Transverse momentum dependent parton distribution functions (TMD PDFs) encode 
information about the intrinsic motion of quarks in the nucleon. We present 
first calculations on the lattice, based on MILC gauge configurations and 
propagators from LHPC. The resulting spin-dependent densities exhibit visible 
dipole deformations in the nucleon. Moreover, the lattice data agrees with 
the assumption of factorization in longitudinal and transverse quark momentum. 
For our exploratory calculations we employ a non-local operator with a 
non-perturbatively renormalized straight Wilson line. A more elaborate 
operator geometry is needed for quantitative comparisons to azimuthal 
asymmetries observable in experiments, such as the Sivers effect in 
semi-inclusive deeply inelastic scattering.