Preliminary Calculation of αS from Green Functions with Dynamical Quarks

We present preliminary results on the computation of the QCD running coupling constant in the scheme and Landau gauge with two flavours of dynamical Wilson quarks. Gluon momenta range up to about 7 GeV (β = 5.6, 5.8 and 6.0) with a constant dynamical-quark mass. This range already allows to exhibit some evidence for a sizable 1/μ2 correction to the asymptotic behaviour, as in the quenched approximation, although a fit without power corrections is still possible with a reasonable χ2. Following the conclusions of our quenched study, we take into account 1/μ2 correction to the asymptotic behaviour. We find = 264(27) MeV × [a−1(5.6,0.1560)/2.19 GeV], which leads to αs(MZ) = 0.113(3)(4). The latter result has to be taken as a preliminary indication rather than a real prediction in view of the systematic errors still to be controlled. Still, being two sigmas below the experimental result makes it very encouraging.