Measurement of the tau lepton lifetime

The tau lepton lifetime has been measured using two independent techniques; an impact parameter analysis of the 1-prong decays and a decay length analysis of the 3-prong decays. Approximately 5 000 Z0 decays to τ+τ− have been selected from the data collected with the OPAL detector at LEP during 1990. The results of the two statistically independent measurements are, respectively, τ1=0.293 ± 0.013 (stat.)±0.013 (syst.) ps and τ3=0.327±0.017 (stat.)±0.011 (syst.) ps. After combining the statistical and systematic errors for each analysis in quadrature, the weighted average lifetime is calculated to be ττ=0.308 ± 0.013 ps.