A TEST OF OPTIMIZED PERTURBATIVE QCD TO ${\mathcal O}(\alpha _s^2)$ AND ${\mathcal O}(\alpha_s^3)$ FROM Z0 AND τ DECAYS, AND A METHOD TO DEAL WITH THE RENORMALIZATION SCALE AMBIGUITY

Abstract

A QCD analysis of the published LEP data on 11 observables measured in the Z0 and τ decays is performed in order to probe the renormalization scale optimization of perturbative QCD to [Formula: see text] and [Formula: see text]. The explicit dependence of the fundamental QCD parameter [Formula: see text] on the renormalization scale μ2 is extracted from the data. The theoretical predictions for the optimized scale are calculated using various QCD-inspired procedures, and are compared to the experimental results. An experimental procedure is presented to deal with the renormalization scale ambiguity in the determination of αs. Applying this procedure to 11 observables, we obtain αs(Mz0)=0.114±0.004 as our final result.