Measurement of the Tau Lepton Lifetime at CLEO II

The τ lepton lifetime has been measured using τ⁺τ^- pairs in which one or both of the τ's decays into three charged particles. The method employed measures the displacement of the reconstructed tau decay vertices using 2 fb ^-1 of data, corresponding to approximately 2 million produced tau pairs, at energies near the(4 S). This data was collected with the CLEO-II detector at the Cornell Electron-Positron Storage Ring (CESR). For events where both τs decayed to 3 charged tracks, the measured lifetime was τ _τ=(2.85 ± 0.13 ± 0.10) × 10 ^-13 s. The measure lifetime for events where one τ decayed into three charged track, and the other decayed into a single charged track was τ _τ=(2.91 ± 0.04 ± 0.07) × 10 ^-13 s.