Measurement of the B0 and B+ lifetimes

From a data sample of approximately 240 000 hadronic Z0 decays recorded during 1991 a sample of about 130 semileptonic B hadron decays containing a D0, D+ or D∗+ has been isolated. Using silicon microvertex detector information the decay vertices in these events have been reconstructed. The average B hadron lifetime of the mix of B hadrons in this event sample is measured to be 1.51−0.14+0.16±0.11 ps. From the distribution of decay times in the different samples the lifetimes of the B0 and B+ mesons are determined to be 1.51−0.23−0.14+0.24+0.12 ps and 1.51−0.28−0.14+0.30+0.12 ps, respectively. The measured ratio of the B+ to B0 lifetimes of 1.00−0.25+0.33±0.08 supports expectations that the lifetimes are similar.