Light quarks with twisted mass fermions

TL;DR

This paper explores Wilson twisted mass fermions in quenched QCD, demonstrating that a specific critical mass definition enables reliable simulations at small quark and pion masses with controlled discretization errors.

Contribution

It introduces an improved method for defining the critical mass in twisted mass fermions, allowing accurate simulations at low quark masses with minimal lattice artifacts.

Findings

Reliable simulations down to m_pi ≈ 250 MeV

Automatic O(a) improvement achieved

Controlled O(a^2) cutoff effects

Abstract

We investigate Wilson twisted mass fermions in the quenched approximation using different definitions of the critical bare quark mass m_c to realize maximal twist and, correspondingly, automatic O(a) improvement for physical observables. A particular definition of m_c is given by extrapolating the value of m_c obtained from the PCAC relation at non-vanishing bare twisted quark mass mu to mu=0. Employing this improved definition of the critical mass the Wilson twisted mass formulation provides the possibility to perform reliable simulations down to very small quark masses with correspondingly small pion masses of m_pi \simeq 250 MeV, while keeping the cutoff effects of O(a^2) under control.