Measurement of the Bs0 lifetime

The lifetime of the Bs0 has been measured in a data sample of 8890000 hadronic events recorded with the ALEPH detector at LEP. After background subtraction 30.8 ± 6.9 events are attributed to the semileptonic decay of the Bs0 to a Ds− and an opposite-sign lepton. A maximum-likelihood fit to the distribution of the proper times of these events yields a Bs0 lifetime of τBs = 1.92−0.35+0.45 ± 0.04 ps.