Chiral extrapolation of lattice moments of proton quark distributions - art. no. 172001

We present the resolution of a long-standing discrepancy between the moment s of parton distributions calculated from lattice QCD and their experimenta l values. We propose a simple extrapolation formula for the moments of the nonsinglet quark distribution u - d, as a function of quark mass, which emb odies the general constraints imposed by the chiral symmetry of QCD. The in clusion of the leading nonanalytic behavior leads to an excellent descripti on of both the lattice data and the experimental values of the moments.