Twist-two matrix elements at finite and infinite volume

TL;DR

This paper provides one-loop calculations of twist-two matrix elements in baryon chiral perturbation theory, analyzing finite volume effects relevant for lattice QCD simulations and their impact on structure function computations.

Contribution

It offers a comprehensive analysis of finite volume effects on twist-two matrix elements in various QCD frameworks, aiding lattice QCD data interpretation.

Findings

Finite volume effects are around 5-10% in current calculations.

Volume effects are larger in quenched QCD.

Results facilitate extrapolation from finite to infinite volume in lattice studies.

Abstract

We present one-loop results for the forward twist-two matrix elements relevant to the unpolarised, 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|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.