Perturbative and nonperturbative renormalization in lattice QCD

We investigate the perturbative and nonperturbative renormalization of composite operators in lattice QCD restricting ourselves to operators that are bilinear in the quark fields (quark-antiquark operators). These include operators which are relevant to the calculation of moments of hadronic structure functions. The nonperturbative computations are based on Monte Carlo simulations with two flavors of clover fermions and utilize the Rome-Southampton method also known as the regularization independent momentum or RI-MOM scheme. We compare the results of this approach with various estimates from lattice perturbation theory, in particular, with recent two-loop calculations.