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Preliminary Calculation of 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 ( 5.6,
5.8 and 6.0) with a constant dynamical-quark mass. This range already allows to
exhibit some evidence for a sizable correction to the asymptotic
behaviour, as in the quenched approximation, although a fit without power
corrections is still possible with a reasonable . Following the
conclusions of our quenched study, we take into account correction to
the asymptotic behaviour. We find , which leads to
. 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.Comment: 14 pages, 3 figs., 2 tabs., revte