A measurement of the gluon splitting rate into bb̄ pairs in hadronic Z decays

Abstract A measurement of the fraction of hadronic Z decays in which a gluon splits into a b b pair, g b b , is presented using data collected by ALEPH from 1992 to 1995 at the Z resonance. The selection is based on four-jet events. Events are selected by means of topological cuts and a lifetime tag. The result is g b b =(2.77±0.42 (stat)±0.57 (syst))×10 −3 .