$\Lambda_{QCD}$ from gluon and ghost propagators

TL;DR

This paper estimates the QCD scale parameter $\Lambda_{QCD}$ by comparing lattice QCD calculations of gluon and ghost propagators with perturbative results, revealing a gluon condensate contribution.

Contribution

It provides a lattice QCD determination of $\Lambda_{QCD}$ and evidence for a dimension-two gluon condensate affecting the ghost-gluon vertex.

Findings

A power correction is necessary for matching lattice and perturbative results.

The gluon condensate value is higher than in quenched QCD.

The study connects lattice data with continuum perturbation theory.

Abstract

Fundamental quantities of QCD, such as the strong coupling and $\Lambda_{QCD}$, are studied in the framework of lattice QCD with $N_f=2$ twisted mass fermions. In particular, the contact between lattice and continuous calculations is made by comparing the renormalized ghost-gluon vertex in MOM scheme with 4-loop perturbative results. A power correction is needed in order to have agreement between the two descriptions. This suggests the presence of a dimension-two $\VEV{A^2}$ gluon condensate whose value is found to be higher than in the quanched case.