Production rate and decay lifetime measurements ofBs0 mesons at LEP usingDs andϕ mesons

The study of the properties of inclusive production ofDs mesons and of events in which a ϕ and a muon are present in the same jet provides two independent measurements of the probability,fsw, for a heavy quark to hadronize into a strangeB orD meson. The data sample analysed corresponds to 243,000 hadronicZ0 decays. The combined value of these measurements isfsw=0.19±0.06±0.08. From the flight distance distributions ofDs and of (ϕ-lepton) secondary vertices, with the lepton emitted at high transverse momentum relative to the jet axis, two values are obtained for theBs0 meson lifetime. Combining these measurements with a previous result based on the study ofDs-μ events, theBs0 meson lifetime is measured to be: 0.96±0.37 ps.