Measurement of the multiplicity of gluons splitting to bottom quark pairs in hadronic Z0 decays

An inclusive measurement of the average multiplicity of $b \bar b$ pairs from gluons, \gb, in hadronic $Z^0$ events collected by the DELPHI experiment at LEP, is presented. A counting technique, based on jet $b$-tagging in 4-jet events, has been used. Looking for secondary bottom production in events with production of any primary flavour, by requiring two $b$-tagged jets in well defined topological configurations, gave gb = (0.21 \pm 0.11(stat) \pm 0.09 (syst) )\%. This result was checked with a different method designed to select events with four $b$ quarks in the final state. Agreement within the errors was found.