Quark propagator and vertex: systematic corrections of hypercubic artifacts from lattice simulations

TL;DR

This paper introduces a new, efficient method to systematically eliminate hypercubic artifacts in lattice QCD simulations of the quark propagator and vertex functions, enabling more accurate high-momentum analyses.

Contribution

A novel systematic expansion method on hypercubic invariants that outperforms previous 'democratic' approaches for removing lattice artifacts.

Findings

Hypercubic artifacts are significantly large in the studied lattice simulations.

Overlap actions exhibit larger artifacts than clover actions.

Propagators show larger artifacts than vertex functions.

Abstract

This is the first part of a study of the quark propagator and the vertex function of the vector current on the lattice in the Landau gauge and using both Wilson-clover and overlap actions. In order to be able to identify lattice artifacts and to reach large momenta we use a range of lattice spacings. The lattice artifacts turn out to be exceedingly large in this study. We present a new and very efficient method to eliminate the hypercubic (anisotropy) artifacts based on a systematic expansion on hypercubic invariants which are not SO(4) invariant. A simpler version of this method has been used in previous works. This method is shown to be significantly more efficient than the popular ``democratic'' methods. It can of course be applied to the lattice simulations of many other physical quantities. The analysis indicates a hierarchy in the size of hypercubic artifacts: overlap larger than clover and propagator larger than vertex function. This pleads for the combined study of propagators and vertex functions via Ward identities.