Decay properties of tau leptons measured at the Z° resonance

Abstract

From 2540 Z ° ---, r+r - events, we determine the inclusive decay branching fractions of the r-lepton into one and three charged particles to be 0.856 ± 0.006 (stat.) + 0.003 (syst.) and 0.144 + 0.006 (stat.) 4- 0.003 (syst.), respectively. The leptonic branching fractions are measured to be 0.175 + 0.008 (stat.) 5:0.005 (syst.) for r ---, ltuuur and 0.177 4- 0.007 (stat.) 4- 0.006 (syst.) for r ~ eueur. We determine the r lifetime both from three-prong decays using the decay length and from one-prong decays using the impact parameter. The results from the two independent methods agree and yield a combined value of [0.309 4- 0.023 (stat.)+ 0.030 (syst.)] × 10-1as.