We report on recent results for the pion matrix element of the twist-2 operator corresponding to the average momentum of non-singlet quark densities. For the first time finite volume effects of this matrix element are investigated and come out to be surprisingly large. We use standard Wilson and non-perturbatively improved clover actions in order to control better the extrapolation to the continuum limit. Moreover, we compute, fully non-perturbatively, the renormalization group invariant matrix element, which allows a comparison with experimental results in a broad range of energy scales. Finally, we discuss the remaining uncertainties, the extrapolation to the chiral limit and the quenched approximation.
@article{arxiv.hep-lat/0309126,
title = {Pion parton distribution functions from lattice QCD},
author = {I. Wetzorke and M. Guagnelli and K. Jansen and F. Palombi and R. Petronzio and A. Shindler},
journal= {arXiv preprint arXiv:hep-lat/0309126},
year = {2009}
}