Measurement ofτLifetime and Branching Ratios

Precise results are reported for the τ-lepton lifetime and several τ branching ratios obtained with the MAC detector operating at PEP at √s=29 GeV. We find τ_τ=(3.15±0.36±0.4)×10^-13 sec. Results for the topological branching ratios B₁, B₃, B₅ (τ decaying into 1, 3, 5 charged particles) are B₃≡1-B₁=0.133±0.003±0.006 and B₅<0.0017 at the 95% confidence level. The fraction of all three-prong decays unaccompanied by π⁰'s is found to be 0.61±{}0.03±{}0.05.