QCD analysis of the tau hadronic width

The total τ hadronic width can be accurately calculated using analyticity and the operator product expansion. The theoretical analysis of this observable is updated to include all available perturbative and non-perturbative corrections. Experimental measurements of τ decay rates are used to determine with high precision the QCD running coupling constant at the scale of the τ mass. The analysis is also used to study the present discrepancy between the experimental measurements of the leptonic branching fractions of the τ and its total lifetime. © 1992.