Resummation of (ß₀α_s)ⁿ corrections in QCD: techniques and applications to the τ hadronic width and the heavy quark pole mass

We propose to resum exactly any number of one-loop vacuum polarization insertions into the scale of the coupling of lowest order radiative corrections. This makes maximal use of the information contained in one-loop perturbative corrections combined with the one-loop running of the effective coupling and provides a natural extension of the familiar BLM scale-fixing prescription to all orders in the perturbation theory. It is suggested that the remaining radiative corrections should be reduced after resummation. In this paper we implement this resummation by a dispersion technique and indicate a possible generalization to incorporate two-loop evolution. We investigate in some detail higher-order perturbative corrections to the τ-decay width and the pole mass of a heavy quark. We find that these corrections tend to reduce α_s(m_τ) determined from τ-decays by approximately 10% and increase the difference between the bottom pole and MS-renormalized mass by 30%.