Measurement of the tau lifetime

We have used a high-resolution drift chamber in the Mark II detector at the SLAC storage ring PEP to measure the lifetime of τ leptons produced in $e^{+}$ $e^{\mathrm{-}}$ annihilations at 29 GeV. Based on the flight-path distribution of 807 three-prong τ decays, the lifetime is found to be (2.88±0.16 ±0.17)×${10}^{\mathrm{-}13}$ sec, in agreement with expectations for e-μ-τ universality.