A MEASUREMENT OF ELECTRON PRODUCTION IN HADRONIC Z0 DECAYS AND A DETERMINATION OF GAMMA(Z0-]B(B)BAR)

The production rate of electrons with momentum p > 4 GeV/c and large momentum transverse to the jet containing the electron has been measured in 136 000 hadronic decays of the Z0 recorded with the OPAL detector at LEP in 1990. The dominant source of these electrons is the semileptonic decay of hadrons containing b quarks. If we assume that the semileptonic branching fraction of b hadrons produced on the Z0 resonance is the same as the branching fraction measured at the UPSILON(4S) resonance, we determine GAMMA(bbBAR) = 394 +/- 13 +/- 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 of b hadron semileptonic decay by taking into account the correlation between the model dependence of the branching fractions measured at the UPSILON(4S) and of our kinematic acceptance for electrons.