Speaker: Christian Wiese (DESY/HU)
Title: The Calculation of Parton Distributions from Lattice QCD
Abstract: Although parton distribution functions are the fundamental objects describing the inner structure of hadrons, they were so far not calculated from first principles, since this would require a non-perturbative approach to QCD.
Certainly, a most promising candidate for such a calculation is lattice QCD, which performed successful computations of hadronic spectra and form factors but not of distributions themselves. The reason for this is that quark distributions are given by light-cone correlations and light-like distances are not accessible on an Euclidean lattice.
A recent proposal however, allows the light-cone distributions to be extracted from purely spatial correlations, being thus accessible by lattice methods. In order to test the feasibility of this method, we present the latest results of our effort to perform an ab-initio lattice calculation of the non-singlet combination for the momentum, helicity and transversity distributions of the nucleon.
Matching the spatial quasi-distributions with the physical distributions requires a large nucleon momentum in the lattice calculation, which usually results in a poor signal-to-noise ratio. We will thus explore the application of a newly proposed momentum smearing of the nucleon fields and present first results which we compare to our previous results.