Production rates of bb-bar quark pairs from gluons and bb-(bar)bb-(bar) events in hadronic Z~0 decays

摘要

The rates are measured per hadronic Z~0 decay for gluon splitting to bb-bar quark pairs, g_(bb-bar), and of events containing two bb-bar quark pairs, g_(4b), using a sample of four-jet events selected from data collected with the OPAL detector. Events with an enhanced signal of gluon splitting to bb-bar quarks are selected if two of the jets are close in phase-space and contain detached secondary vertices. For the event sample containing two bb-bar quark pairs, three of the four jets are required to have a significantly detached secondary vertex. Information from the event topology is combined in a likelihood fit to extract the values of g_(bb-bar) and g_(4b), namely g_(bb-bar) = (3.07 ± 0.53(stat)± 0.97(syst)) * 10~(-3), g_(4b) = (0.36 37L?0.17(stat) ±0.27(syst)) * 10~(-3).