Measurement of heavy quark forward-backward asymmetries and average B mixing using leptons in multihadronic events

A measurement of the forward-backward asymmetries of e+e-→Z0→b anti b and e+e-→Z0→c anti c using electrons and muons produced in semileptonic decays of bottom and charm hadrons is presented. Two new variables designed to optimize flavour separation are used in a maximum likelihood fit to a sample of events containing one or two identified leptons, allowing the simultaneous extraction of the b and c quark forward-backward asymmetries as well as the average B0-B0 mixing. Using all data collected by OPAL up to the end of 1994, the asymmetries are measured to be: AbFB=(5.5±2.4±0.3)% and AcFB=(7.5±3.4±0.6)% at left angle √s right angle =89.52 GeV, AbFB=(9.06±0.51±0.23)% and AcFB=(6.00±0.67±0.52)% at left angle √s right angle =91.24 GeV, AbFB=(11.7±2.0±0.3)% and AcFB=(14.1±2.8±0.9)% at left angle √s right angle =92.94 GeV. For the average B0-B0 mixing a value of: anti χ=0.1107±0.0062±0.0055, is obtained, where in each case the first error is statistical and the second systematic. (orig.)