Testing QCD with hypothetical tau leptons - art. no. 037501.

We construct new phenomenological tests of perturbative QCD by considering a hypothetical tau lepton of arbitrary mass which decays hadronically throu gh the electromagnetic current. Its hadronic branching ratio can be compute d directly as an integral over the e(+)e(-) annihilation cross section rati o, Re+e-. More generally, we can design a set of commensurate scale relatio ns which test the applicability and self-consistency of leading twist QCD p redictions by varying the weight function away from the form associated wit h the V-A decay of the physical tau. This method allows the wide range of R e+e- data (or other similar observables which define an effective charge) t o be used as renormalization scheme and scale invariant probes of QCD. [S05 56-2821(99)05713-6].