Updated measurement of the τ lifetime

We present an update of our measurement of the τ lepton lifetime, using data taken during 1992 and 1993 with the OPAL detector at LEP. The lifetime is determined from analyses of the impact parameters of tracks from τ decays to a single charged particle, and the reconstructed decay lenghts from the τ decays to three charged particles. With the added statistics (which increase the τ pair event sample size by more than a factor of four over our 1990 and 1991 data sample), the updated lifetime measurement is: ττ = 288.8 ± 2.2 (stat) ± 1.4 (sys) fs. When combined with world-average measurements of the tau leptonic branching fractions (assuming e-μ universality), the ratio of charged-current couplings is: ( g τ g μ ) = 1.005 ± 0.007 , in agreement with the hypothesis of τ-μ charged-current universality.