Measurement of the average B hadron lifetime in Z0 decays

Abstract A sample of 689 muon candidates and 665 electron candidates identified in multihadronic Z 0 decays has been used to measure the average B hadronlifetime. These data were recorded with the OPAL detector during 1990. Maximum likelihood fits to the distributions of the lepton impact parametersyield an average B hadronlifetime of τ b = 1.37 ± 0.07 ± 0.06 ps, where the first error is statistical and the second systematic. This result is a weighted average over the semileptonic branching fractionsand production rates of the B hadronsproduced in Z 0 decays.