A lattice evaluation of four-quark operators in the nucleon

TL;DR

This paper evaluates four-quark operators in the nucleon using lattice QCD, revealing that certain twist-four contributions are minimal, which impacts understanding of nucleon structure and diquark correlations.

Contribution

It provides the first lattice QCD calculation of nucleon matrix elements of four-quark operators, avoiding mixing issues through flavor symmetry considerations.

Findings

Twist-four contributions are very small for some flavor combinations.

Results suggest twist-four effects are negligible compared to leading contributions.

Provides insights into the diquark structure of the nucleon.

Abstract

Nucleon matrix elements of various four-quark operators are evaluated in quenched lattice QCD using Wilson fermions. Some of these operators give rise to twist-four contributions to nucleon structure functions. Furthermore, they bear valuable information about the diquark structure of the nucleon. Mixing with lower-dimensional operators is avoided by considering appropriate representations of the flavour group. We find that for a certain flavour combination of baryon structure functions, twist-four contributions are very small. This suggests that twist-four effects for the nucleon might be much smaller than m_p^2/Q^2.