Ghost-gluon coupling, power corrections and $Λ_overline MS$ from twisted-mass lattice QCD at Nf=2
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 $Λ_overlineMS$ 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 $\VEVA^2$ gluon condensate. The effect due to the dynamical quark mass in the determination of $\Lams$ is discussed.