O(a^2) cutoff effects in lattice Wilson fermion simulations

TL;DR

This paper investigates the large discretization artifacts in maximally twisted lattice QCD simulations, attributing them to O(a^2) effects linked to the pseudoscalar density matrix element, influenced by chiral symmetry breaking.

Contribution

It offers a new interpretation of cutoff effects as O(a^2) artifacts proportional to a specific matrix element, enhancing understanding of lattice QCD discretization errors.

Findings

Discretization artifacts are proportional to the pseudoscalar density matrix element.

The size of effects is larger than expected from Lambda_QCD scale.

Chiral symmetry breaking significantly influences cutoff effects.

Abstract

In this paper we propose to interpret the large discretization artifacts affecting the neutral pion mass in maximally twisted lattice QCD simulations as O(a^2) effects whose magnitude is roughly proportional to the modulus square of the (continuum) matrix element of the pseudoscalar density operator between vacuum and one-pion state. The numerical size of this quantity is determined by the dynamical mechanism of spontaneous chiral symmetry breaking and turns out to be substantially larger than its natural magnitude set by the value of Lambda_QCD.