Perturbative QCD relations inspired by hypothetical tau leptons

Abstract

We review our recent works on tests of perturbative QCD, inspired by the relation between the hadronic decay of the τ lepton and the e+e- annihilation into hadrons. First, we present a set of commensurate scale relations that probe the self-consistency of leading-twist QCD predictions for any observable which defines an effective charge. These tests are independent of the renormalization scheme and scale, and are applicable over wide data ranges. As an example we apply this approach to Re+e-. Second, using a differential form of these conmensurate scale relations, we present a method to measure the QCD Gell-Mann-Low ψ function.