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

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 $\text{VEV}{A}^2$ gluon condensate. The effect due to the dynamical quark mass in the determination of $\text{Lams}$ is discussed.

Comments: 33 pages, 6 figs