Production rates of b.hivin.b quark pairs from gluons and b.hivin.bb.hivin.b events in hadronic Z0 decays.

The rates were measured per hadronic Z0 decay for gluon splitting to b.hivin.b quark pairs, gb.hivin.b, and of events contg. two b.hivin.b quark pairs, g4b, using a sample of four-jet events selected from data collected with the OPAL detector. Events with an enhanced signal of gluon splitting to b.hivin.b quarks were selected if two of the jets are close in phase space and contain detached secondary vertexes. For the event sample contg. two b.hivin.b quark pairs, three of the four jets are required to have a significantly detached secondary vertex. Information from the event topol. was combined in a likelihood fit to ext. the values of gbb and g4b, i.e. gb.hivin.b = (3.07 +- 0.53(stat) +- 0.97(syst)) * 10-3 and g4b = (0.36 +- 0.17(stat) +- 0.27(syst)) * 10-3. [on SciFinder (R)]