Nucleon structure with partially twisted boundary conditions

Abstract

A large number of fundamental hadron structure observables are defined in the limit of vanishing momentum transfer, but at the same time cannot be directly extracted from forward matrix elements. This is a challenge for current lattice QCD simulations, where volumes and lattice spacings are such that the lowest accessible non-zero momentum transfers are ∼ 0.15 GeV2 and larger, making in general model-dependent extrapolations to the forward limit necessary. Twisted boundary conditions for the valence quarks provide the opportunity to study hadronic matrix elements in dynamical lattice QCD calculations for almost arbitrary hadron momenta. We present preliminary results for the Dirac- and Pauli form factors and the form factors of the energy momentum tensor for the nucleon very close to the forward limit, using partially twisted boundary conditions. The calculations are based on gauge configurations generated with two flavors of clover-improved Wilson fermions.