Decay properties of tau leptons measured at the Z 0 resonance

From 2540 Z 0 → τ +τ - events, we determine the inclusive decay branching fractions of the τ-lepton into one and three charged particles to be 0.856 ± 0.006 (stat.) ± 0.003 (syst.) and 0.144 ± 0.006 (stat.) ± 0.003 (syst.), respectively. The leptonic branching fractions are measured to be 0.175 ± 0.008 (stat.) ± 0.005 (syst.) for τ → μν μν τ and 0.177 ± 0.007 (stat.) ± 0.006 (syst.) for τ → eν eν τ. We determine the τ 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 ± 0.023 (stat.) ± 0.030 (syst.)] × 10 -12s.