A measurement of electron production in hadronicZ0 decays and a determination of\(\Gamma (Z^0 \to b\bar b)\)

The production rate of electrons with momentump>4 GeV/c and large momentum transverse to the jet containing the electron has been measured in 136000 hadronicdecays of theZ0 recorded with the OPAL detector at LEP in 1990. The dominant source of these electrons is the semileptonic decayof hadronscontainingb quarks. If we assume that the semileptonic branching fractionofb hadronsproduced on theZ0 resonance is the same as the branching fractionmeasured at the ϒ(4S) resonance, we determine\(\Gamma _{b\bar b} = 394 \pm 13 \pm 32\) MeV, where the first error is statistical and the second error is systematic. The sensitivity of the result to this assumption is discussed. We have reduced the dependence of our result on the model ofb hadron semileptonic decayby taking into account the correlation between the model dependence of the branching fractionsmeasured at the ϒ(4S) and of our kinematic acceptance for electrons.