Overlap valence quarks on a twisted mass sea: a case study for mixed action Lattice QCD

TL;DR

This paper investigates a mixed action Lattice QCD approach combining Wilson twisted mass sea and overlap valence fermions, demonstrating continuum limit behavior and extracting low energy constants related to unitarity violations.

Contribution

It shows the overlap Dirac operator's locality in the continuum limit and establishes matching conditions for consistent physical results in a mixed action setup.

Findings

Overlap Dirac operator is point-like local in the continuum limit.

Consistent continuum limit for pion decay constant and baryon masses.

Extraction of low energy constants characterizing unitarity violations.

Abstract

We discuss a Lattice QCD mixed action investigation employing Wilson maximally twisted mass sea and overlap valence fermions. Using four values of the lattice spacing, we demonstrate that the overlap Dirac operator assumes a point-like locality in the continuum limit. We also show that by adopting suitable matching conditions for the sea and valence theories a consistent continuum limit for the pion decay constant and light baryon masses can be obtained. Finally, we confront results for sea-valence mixed meson masses and the valence scalar correlator with corresponding expressions of chiral perturbation theory. This allows us to extract low energy constants of mixed action chiral perturbation which characterize the strength of unitarity violations in our mixed action setup.