Computation of the strong coupling in QCD with two dynamical flavors

We present a non-perturbative computation of the running of the coupling αs in QCD with two flavors of dynamical fermions in the Schrödinger functional scheme. We improve our previous results by a reliable continuum extrapolation. The Λ-parameter characterizing the high-energy running is related to the value of the coupling at low energy in the continuum limit. An estimate of Λr0 is given using large-volume data with lattice spacings a from 0.07fm to 0.1fm. It translates into ΛMS¯(2)=245(16)(16)MeV [assuming r0=0.5fm]. The last step still has to be improved to reduce the uncertainty.