Ghost-gluon coupling, power corrections and $\Lambda_{\overline {\rm MS}}$ from twisted-mass lattice QCD at Nf=2

TL;DR

This paper non-perturbatively evaluates the ghost-gluon coupling in lattice QCD with two flavors, introduces a new lattice spacing calibration method, and computes the QCD scale parameter 5MS from the running coupling considering power corrections.

Contribution

It presents a novel lattice spacing calibration method independent of traditional hadron spectrum measurements and analyzes the impact of dynamical quark mass on the determination of 5MS.

Findings

Agreement of lattice spacing calibration with previous estimates

Determination of 5MS consistent with other methods

Analysis of the 5MS value's dependence on quark mass

Abstract

We present results concerning the non-perturbative evaluation of the ghost-gluon running QCD coupling constant from $N_f=2$ twisted-mass lattice calculations. A novel method for calibrating the lattice spacing, independent of the string tension and hadron spectrum is presented with results in agreement with previous estimates. The value of $\Lambda_{\overline{MS}}$ is computed from the running of the QCD coupling only after extrapolating to zero dynamical quark mass and after removing a non-perturbative OPE contribution that is assumed to be dominated by the dimension-two $\VEV{A^2}$ gluon condensate. The effect due to the dynamical quark mass in the determination of $\Lams$ is discussed.