R. Akers et al., MEASUREMENT OF THE TIME-DEPENDENCE OF B(D)(0)[--]B(OVER-BAR)(0)(D) MIXING USING LEPTONS AND D-ASTERISK+ - MESONS/, Physics letters. Section B, 336(3-4), 1994, pp. 585-598
Data collected with the OPAL detector at LEP during 1990-1993 are used
to measure the time dependence of B(d)0 <--> BBAR(d)0 mixing. From a
sample of 153 +/- 12 events with a charged D and a lepton in the oppo
site hemisphere, we measure the B(d)0 <--> BBAR(d)0 oscillation freque
ncy to be DELTAm(d) = 0.57 +/- 0.11 (stat.) +/- 0.02 (syst.) ps-1. Thi
s corresponds to an oscillation parameter of x(d) = DELTAm(d)tau(B)(d)
0 = 0.82 +/- 0.16 (stat.) +/- 0.03 (syst.) +/- 0.09 (syst. tau(B)(d)0)
, where the second systematic uncertainty is due to the error in the m
easured B(d)0 lifetime.