Exploring twisted mass Lattice QCD with the Clover term

TL;DR

This paper demonstrates that adding the Clover term to twisted mass lattice QCD effectively reduces cutoff effects, improves the determination of physical quantities, and mitigates symmetry-breaking artifacts in quenched simulations.

Contribution

The study provides a non-perturbative analysis showing the Clover term's efficiency in suppressing cutoff effects and improving physical observable calculations in twisted mass lattice QCD.

Findings

Clover term reduces large cutoff effects in twisted mass QCD.

Bending phenomenon in pion decay constant is cured.

Improved determination of Z_V and light quark masses.

Abstract

It has been shown that in the twisted mass formulation of Lattice QCD at maximal twist large cutoff effects are generated when the quark mass becomes of O(a Lambda_QCD^2). In general, these effects can be suppressed in two ways: either by choosing the critical quark mass in an "optimal way", or by adding the Clover term to the twisted action. We investigate the second option by performing a quenched lattice QCD simulation with twisted Clover fermions and pion masses as low as 280 MeV. We show that the Clover term is indeed efficient in reducing the large cutoff effects. In particular, the so-called bending phenomenon observed in the determination of the pion decay constant is cured in this way. In addition, by using maximally twisted Clover fermions, we provide a non-perturbative determination of the vector current renormalization constant Z_V as well as of the non-perturbatively renormalized light quark masses. Finally, we calculate the connected contribution to the charged-neutral pseudoscalar meson mass splitting, finding that the introduction of the Clover term in the twisted action is also beneficial, in the quenched approximation, in reducing cutoff effects related to the isospin symmetry breaking at finite lattice spacing.