Ghost-gluon coupling, power corrections, and Λ(MS)over-bar from twisted-mass lattice QCD at Nf=2

We present results concerning the nonperturbative 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((MS) over bar) is computed from the running of the QCD coupling only after extrapolating to zero dynamical quark mass and after removing a nonperturbative operator-product expansion contribution that is assumed to be dominated by the dimension-two < A(2)> gluon condensate. The effect due to the dynamical quark mass in the determination of Lambda((MS) over bar) is discussed.