Computation of the strong coupling in QCD with two dynamical flavors

We present a non-perturbative computation of the running of the coupling alpha(s) in QCD with two flavors of dynamical fermions in the Schrodinger functional scheme. We improve our previous results by a reliable continuum extrapolation. The Lambda-parameter characterizing the high-energy running is related to the value of the coupling at low energy in the continuum limit. An estimate of Lambda r(0) is given using large-volume data with lattice spacings a from 0.07 fm to 0.1 fm. It translates into (2) Lambda (2)/MS = 245(16)(16) MeV [assuming r(0) = 0.5 fm]. The last step still has to be improved to reduce the uncertainty. (c) 2005 Elsevier B.V. All rights reserved.