Rationale for UV-filtered clover fermions

TL;DR

This paper investigates how UV-filtering techniques improve the behavior of Wilson fermions in lattice QCD, reducing chiral symmetry breaking effects and enhancing the perturbative series.

Contribution

It provides a detailed perturbative analysis of UV-filtered Wilson fermions and demonstrates the effectiveness of filtering combined with clover improvement in non-perturbative simulations.

Findings

Filtering improves perturbative series convergence.

Filtering and clover improvement reduce residual chiral symmetry breaking.

Residual masses are around 0.01 in lattice units.

Abstract

We study the contributions Sigma_0 and Sigma_1, proportional to a^0 and a^1, to the fermion self-energy in Wilson's formulation of lattice QCD with UV-filtering in the fermion action. We derive results for m_{crit} and the renormalization factors Z_S, Z_P, Z_V, Z_A to 1-loop order in perturbation theory for several filtering recipes (APE, HYP, EXP, HEX), both with and without a clover term. The perturbative series is much better behaved with filtering, in particular tadpole resummation proves irrelevant. Our non-perturbative data for m_{crit} and Z_A/(Z_m*Z_P) show that the combination of filtering and clover improvement efficiently reduces the amount of chiral symmetry breaking -- we find residual masses am_{res}=O(10^{-2}).