Chiral Extrapolation of Lattice Moments of Proton Quark Distributions

The behavior of the first three nontrivial moments of the nonsinglet quark distribution u - d in the proton is studied as a function of quark mass in order to guide the extrapolation of lattice QCD calculations to the physical region. We propose a simple extrapolation formula, embodying the general constraints of the chiral symmetry of QCD, which provides an excellent fit to the lattice data and the experimental values for each moment