Measurement of the τ -lepton Lifetime at Belle

Abstract

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 Ï (4S) resonance and 60 MeV below, is τ=(290. 17±0.53(stat)±0.33(syst))×10-15 s. 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% C.L. © 2014 American Physical Society.