Measurement of thebb¯fraction in hadronicZdecays

Abstract

Using isolated leptons reconstructed in the Mark II detector to tag bb¯ events, we measure the fraction of bb¯ events in hadronic ${\mathit{Z}}^0$ decays to be 0.${23}_{\mathrm{-}0.09}^{+0.11\mathrm{}}$, in good agreement with the standard-model prediction of 0.22. We find Γ(Z→bb¯)=0.${43}_{\mathrm{-}0.17}^{+0.21\mathrm{}}$ GeV.