Parton distributions from the lattice Original Research Article

I review the current status of lattice calculations for two selected observables related to nucleon structure: the second moment of the unpolarized parton distribution, 〈x〉u−d, and the first moment of the polarized parton distributions, the non-singlet axial coupling gA. The major challenge is the requirement to extract them sufficiently close to the chiral limit. In the former case, there still remains a puzzling disagreement between lattice data and experiment. For the latter quantity, however, we may be close to obtaining its value from the lattice in the immediate future.