Going chiral: overlap versus twisted mass fermions

TL;DR

This paper compares overlap and twisted mass fermions in lattice QCD, analyzing their behavior near the chiral limit through quenched simulations at a fixed lattice spacing, measuring various physical quantities.

Contribution

It provides a direct comparison of overlap and twisted mass fermions, highlighting their practical capabilities and differences in approaching the chiral limit in lattice simulations.

Findings

Both formulations reach pion masses of about 250 MeV.

Quantities like hadron masses and decay constants are measured for both.

Axial vector renormalization constants are determined for overlap fermions.

Abstract

We compare the behavior of overlap fermions, which are chirally invariant, and of Wilson twisted mass fermions at full twist in the approach to the chiral limit. Our quenched simulations reveal that with both formulations of lattice fermions pion masses of O(250 MeV) can be reached in practical applications. Our comparison is done at a fixed value of the lattice spacing a=0.123 fm. A number of quantities are measured such as hadron masses, pseudoscalar decay constants and quark masses obtained from Ward identities. We also determine the axial vector renormalization constants in the case of overlap fermions.