Measurement of the lifetime of tau-lepton

The lifetime of the τ-lepton is measured using the process e+e−→τ+τ−, where both τ-leptons decay to 3πντ. The result for the mean lifetime, based on 711 fb−1 of data collected with the Belle detector at the ϒ(4S) resonance and 60 MeV below, is τ=(290.17±0.53(stat.)±0.33(syst.))⋅10−15s. The first measurement of the lifetime difference between τ+ and τ− is performed. The upper limit on the relative lifetime difference between positive and negative τ-leptons is |Δτ|/τ<7.0×10−3 at 90% CL.