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An event sample enriched in semileptonic decays of b hadrons is selected using an inclusive lepton selection from approximately 3.0 million hadronic Z 0 decays collected with the OPAL detector. This sample is used to investigate B meson oscillations by reconstructing a proper decay time for the parent of each lepton, using a jet charge method to estimate the production flavour of this parent, and using the lepton charge to tag the decay flavour. We measure the mass difference between the two B 0 d mass eigenstatesFor the B 0 s system, we find ∆m s > 3.1 ps −1 at the 95% confidence level. This limit varies only a little if alternative limit setting approaches are adopted. Regions at higher ∆m s values are also excluded with some methods for setting the limit.By studying the charge symmetry of the B 0 d mixing structure, we are able to constrain possible CP and CPT violating effects. We measure the CP violation parameter Re ǫ B = −0.006 ± 0.010 ± 0.006 and the indirect CPT violating parameter Im δ B = −0.020 ± 0.016 ± 0.006 . If we invoke CPT symmetry, then we obtainRe ǫ B = 0.002 ± 0.007 ± 0.003 .

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The production rates of D * ± mesons in charm and bottom events at centre-of-mass energies of about 91 GeV and the partial width of primary cc pairs in hadronic Z 0 decays have been measured at LEP using almost 4.4 million hadronic Z 0 decays collected with the OPAL detector between 1990 and 1995. Using a combination of several charm quark tagging methods based on fully and partially reconstructed D * ± mesons, and a bottom tag based on identified muons and electrons, the hadronisation fractions of charm and bottom quarks into D * ± mesons have been found to be f (b → D * + X) = 0.173 ± 0.016 ± 0.012 and f (c → D * + X) = 0.222 ± 0.014 ± 0.014 .The fraction of cc events in hadronic Z 0 decays, Γ cc /Γ had = Γ(Z 0 → cc)/Γ(Z 0 → hadrons), is determined to be Γ cc /Γ had = 0.180 ± 0.011 ± 0.012 ± 0.006 .In all cases the first error is statistical, and the second one systematic. The last error quoted for Γ cc /Γ had is due to external branching ratios.