Measurements of Z° bƀ decays and the semileptonic branching ratio BR (b→, ℓ + X)

Abstract

We have measured the decay properties of from a study of inclusive muon and electron events. The average (e and μ) b-quark semileptonic branching ratio has been determined to be BR (b → ℓ + X) = 0.119 ± 0.003 (stat.) ± 0.006 (syst.), assuming the standard model prediction of Γbb = 378 ± 3 MeV. From the ratio of the number of dilepton events to single lepton events, we find BR (b → ℓ + X) = 0.113 ± 0.010 (stat.) ± 0.006 (syst.), without assumptions on Λbb. The partial decay width of the Z0 into has been measured to be Λbb = 385 ± 7 (stat.) ± 11 (syst.) MeV with an additional 19 MeV error from the uncertainty in BR (b → ℓ + X). The average fractional energy of bottom hadrons in events has been determined to be 〈xE〉 = 0.686 ± 0.006 (stat.) ± 0.016 (syst.).