Reducing cutoff effects in maximally twisted lattice QCD close to the chiral limit

TL;DR

This paper demonstrates that by using O(a) improvement or optimal critical mass tuning in maximally twisted lattice QCD, cutoff effects near the chiral limit can be significantly reduced, ensuring smoother continuum extrapolations.

Contribution

The authors prove that specific improvement techniques in twisted lattice QCD diminish infrared divergent cutoff effects, enabling reliable results closer to the chiral limit.

Findings

Cutoff effects are reduced to manageable levels with O(a) improvement.

Smooth continuum extrapolation is possible for quark masses above a^2Λ_QCD^3.

Infrared divergent artifacts are controlled near the chiral limit.

Abstract

When analyzed in terms of the Symanzik expansion, lattice correlators of multi-local (gauge-invariant) operators with non-trivial continuum limit exhibit in maximally twisted lattice QCD ``infrared divergent'' cutoff effects of the type a^{2k}/(m_\pi^2)^{h}, 2k\geq h\geq 1 (k,h integers), which tend to become numerically large when the pion mass gets small. We prove that, if the action is O(a) improved a` la Symanzik or, alternatively, the critical mass counter-term is chosen in some ``optimal'' way, these lattice artifacts are reduced to terms that are at worst of the order a^{2}(a^2/m_\pi^2)^{k-1}, k\geq 1. This implies that the continuum extrapolation of lattice results is smooth at least down to values of the quark mass, m_q, satisfying the order of magnitude inequality m_q >a^2\Lambda^3_{\rm QCD}.