Determination of the τ lifetime in high energy e+e− annihilations

Abstract We have determined the τ lifetime in e + e − annihilations at an average centre of mass energy of 42.5 GeV, using a pressurized drift chamber close to the interaction point. We find the lifetime to be (3.18 −0.75 +0.59 ± 0.56) × 10 −13 s. The charged weak τ coupling constant relative to that of the μ is found to be G τ / G μ = 0.94 −0.09 +0.12 ± 0.09, in good agreement lepton universality.