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

TL;DR

This paper investigates O(a^2) cutoff effects in Wilson fermion simulations, showing they are linked to a large continuum QCD quantity related to chiral symmetry breaking, primarily affecting the neutral pion mass.

Contribution

It reveals the origin and control of O(a^2) cutoff artifacts in Wilson fermion simulations, connecting them to a key continuum QCD parameter and discussing their impact on physical observables.

Findings

O(a^2) effects are tied to a large continuum QCD quantity.

Neutral pion mass is uniquely affected by these cutoff effects.

The impact of O(a^2) effects depends on the critical mass evaluation method.

Abstract

We show that the size of the O(a^2) flavour violating cutoff artifacts that have been found to affect the value of the neutral pion mass in simulations with maximally twisted Wilson fermions is controlled by a continuum QCD quantity that is fairly large and is determined by the dynamical mechanism of spontaneous chiral symmetry breaking. One can argue that the neutral pion mass is the only physical quantity blurred by such cutoff effects. O(a^2) corrections of this kind are also present in standard Wilson fermion simulations, but they can either affect the determination of the pion mass or be shifted from the latter to other observables, depending on the way the critical mass is evaluated.