A tmQCD mixed-action approach to flavour physics

TL;DR

This paper presents a mixed-action lattice QCD approach combining Wilson and twisted mass fermions to improve flavor physics calculations, demonstrating effective matching and scaling of key observables.

Contribution

It introduces a novel mixed-action setup that maintains automatic ${ m O}(a)$ improvement for valence observables in lattice QCD simulations.

Findings

Successful matching of sea and valence quarks in ${N_f}=2+1$ ensembles

Scaling behavior of pseudoscalar decay constants analyzed

Isospin splitting of pseudoscalar meson masses studied

Abstract

We discuss a mixed-action approach in which sea quarks are regularised using non-perturbatively ${\rm O}(a)$ improved Wilson fermions, while a fully-twisted tmQCD action is used for valence quarks. In this setup, automatic ${\rm O}(a)$ improvement is preserved for valence observables, apart from small residual ${\rm O}(a)$ effects from the sea. A strategy for matching sea and valence is set up, and carried out for $N_\mathrm{f}=2+1$ CLS ensembles with open boundary conditions at several simulation points. The scaling of basic light-quark observables such as the pseudoscalar meson decay constant is studied, as well as the isospin splitting of pseudoscalar meson masses.