A study of charm production in beauty decays with the OPAL detector at LEP

The branching ratio of beauty hadrons to final states containing two charm hadrons, Br(b-->D (D) over barX), has been measured using an inclusive method in hadronic Z(0) decays with the OPAL detector at LEP. The impact parameter significance of tracks opposite tagged b-jets is used to differentiate b-->D (D) over barX decays from other decays. The result is Br(b-->D (D) over barX) = (10.0 +/- 3.2 (stat.)(-2.9)(+2.4)(det.)(-9.0)(+10.4) (phys.))%, where "det." is the systematic uncertainty due to the modelling of the detector, and "phys." is the systematic uncertainty due to the modelling of the underlying physics. Using this result, the average number of charm plus anti-charm quarks produced in a beauty quark decay, n(c), is found to be 1.12(-0.10)(+0.11).