L3 measurement of the $\tau$ lepton lifetime

The tau lepton lifetime is measured with the L3 detector at LEP. For the analysis presented here tau pairs produced during 1994 and 1995 around the Z pole are used. The measurement is done by a decay length method for the 3-prong tau decays and by an impact parameter analysis for the 1-prong decays. From the data 6620 3-prong decays are selected, from which a lifetime of tau /sub tau /=291.4+or-3.9 (stat) +or-2.0 (syst) fs is determined. The impact parameter analysis on 58 656 1-prong decays results in a lifetime of tau /sub tau /=290.5+or-2.7 (stat)+or-2.9 (syst) fs. Combination with our previous results gives tau /sub tau /=291.7+or-2.0 (stat)+or-1.8 (syst) fs. These numbers are preliminary. (6 refs).