Measurement of B0B0 mixing in hadronic Z0 decays OPAL collaboration

From a sample of approximately 135 000 hadronic Z0 decays recorded with the OPAL detector, 1 536 events were selected with two lepton candidates, either electrons or muons. A signal for B0B0 mixing was observed using the sign of the lepton charge to tag the charge of the b quark in decaying b-flavoured hadrons. A flavour discriminating variable was constructed from the lepton momentum and its component perpendicular to the jet axis. By fitting …