Moments of singlet parton densities on the lattice in the Schrödinger functional scheme Original Research Article

A non-perturbative computation of the evolution of singlet parton densities without gauge-fixing requires a gauge invariant gluon source operator. Within the Schrödinger Functional scheme (SF), such a source can be defined in terms of path ordered products of gauge links, connected to the time boundaries. In this paper we adopt this definition and perform a one loop lattice computation of the renormalization constants of the twist-2 operators that correspond to the second moment of singlet parton densities. This calculation fixes the connection between the lattice SF scheme where a non-perturbative evaluation of the absolute normalization of singlet parton densities can be made at low energy and the MS scheme where one can extract the experimental values.