Measurements of mixing, and semileptonic branching ratios forb-flavoured hadrons in hadronicZ0 decays

From a sample of about 450 000 hadronicZ0 decays, measurements of the average$$B^0 - \bar B^0 $$ mixing parameter, χ, the branching fraction ofZ0 bosons into hadrons containing bottom quarks,$${{\Gamma (Z^0 \to b\bar b)} \mathord{\left/ {\vphantom {{\Gamma (Z^0 \to b\bar b)} {\Gamma (Z^0 \to hadrons)}}} \right. \kern-\nulldelimiterspace} {\Gamma (Z^0 \to hadrons)}}$$, the average semileptonic branching ratios for such hadrons,B(b→l) andB(b→c→l), and the mean scaled energy of these hadrons, 〈xE〉, are presented. The measurements were obtained using a simultaneous fit to single-lepton and dilepton events collected with the OPAL detector at LEP, including both electrons and muons. The results are where the errors are statistical and systematic, respectively, in each case. The result forB)b→c→l) excludes decays of the typeb→→ℓ.