Evidence for BS0 meson production in Z0 decays

Seven unambiguous events out of a sample of 270 000 Z0 decays, contain in the same jet a Ds meson and a muon at large transverse momentum relative to the jet axis. These events are direct evidence for Bs 0 meson production in hadronic Z0 decays. The production rate of these events, relative to all hadronic Z0 decays is (18 ± 8) × 10-5, this number including the relevant branching fractions of the Bs 0 and Ds. The value of the Bs 0 meson lifetime relative to the average B meson lifetime is measured to be 0.8 ± 0.4.