Strong coupling constant from tau decay within a renormalization scheme invariant treatment - art. no. 036001

We extract a numerical value for the strong coupling constant alpha (s) fro m the tau -lepton decay rate into non-strange particles. A new feature of o ur procedure is the explicit use of renormalization scheme invariance in an alytical form in order to perform the actual analysis in a particular renor malization scheme. For the reference coupling constant in the (MS) over bar scheme we obtain alpha (s)(M-tau) = 0.3184+/-0.0060(expt) which correspond s to alpha (s)(M-Z) = 0.1184+/-0.0007(expt)+/- 0.0006(hq) (mass). This new numerical value is smaller than the standard value from tau data quoted in the literature and is closer to alpha (s)(M-Z) values obtained from high en ergy experiments.