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.