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Calculation of the moments of generalized parton distributions in lattice QCD requires more powerful techniques than those previously used to calculate the moments of structure functions. Hence, we present a novel approach that exploits the full information content from a given lattice configuration by measuring an overdetermined set of lattice observables to provide maximal statistical constraints on the generalized form factors at a given virtuality t. In an exploratory investigation using unquenched QCD configurations at intermediate sea quark masses, we demonstrate that our new technique is superior to conventional methods and leads to reliable numerical signals for the n=2 flavor singlet generalized form factors up to 3GeV^2. The contribution from connected diagrams in the flavor singlet sector to the total quark angular momentum is measured to an accuracy of the order of 1%.
Hägler et al. (Mon,) studied this question.