Twist-two matrix elements at finite and infinite volume

We present one-loop results for the forward twist-two matrix elements relevant to the unpolarized, helicity and transversity baryon structure functions, in partially-quenched (N-f = 2 and N-f = 2 + 1) heavy baryon chiral perturbation theory. The full-QCD limit can be straightforwardly obtained from these results and we also consider SU(2 vertical bar 2) quenched QCD. Our calculations are performed in finite volume as well as in infinite-volume. We discuss features of lattice simulations and investigate finite volume effects in detail. We find that volume effects are not negligible, typically around 5%-10% in current partially-quenched and full-QCD calculations, and are possibly larger in quenched QCD. Extensions to the off-forward matrix elements and potential difficulties that occur there are also discussed.