2 research outputs found

    Determination of |V(ub)| from the measurement of the inclusive charmless semileptonic branching ratio of b hadrons

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    From a study of the kinematic properties of the final state produced in the semileptonic decays b --> Xlv(l), the inclusive charmless semileptonic branching ratio of b hadrons is measured. With a sample of 3.6 million hadronic Z decays recorded between 1992 and 1995 with the ALEPH detector at LEP, the value Br(b --> X(u)lv(l)) is determined to be (1.73 +/- 0.55(stat) +/- 0.55(syst)) x 10(-3), where X(u) represents any charmless hadronic state and b is a mixture of b hadrons weighted by their production rates. This measurement yields the result |V-ub|(2) = (18.68 +/- 5.94(stat) +/- 5.94(syst) +/- 1.45(HQE)) x 10(-6) where the last error comes from the conversion of the branching ratio to the CKM matrix element squared

    Measurement of the Z resonance parameters at LEP

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    The properties of the Z resonance are measured from the analysis of 4.5 million Z decays into fermion pairs collected with the ALEPII detector at LEP. The data are consistent with lepton universality. The resonance parameters are measured to be M(Z) = (91.1885 +/- 0.0031) GeV/c(2), Gamma(Z) = (2.4941 +/- 0.0043) GeV, sigma(had)(0) = (41.559 +/- 0.058) nb and, combining the three lepton flavours, R(l) = 20.725 +/- 0.039. The corresponding number of light neutrino species is N(v) = 2.983 +/- 0.013 and the strong coupling constant is alpha(s)(M(Z)) = 0.114 +/- 0.004 +/- 0.002(QCD) + 0.005 log(10) [M(H)/150 GeV/c(2)]. The lepton pair forward-backward asymmetry is measured to be A(FB)(0,l) = 0.0173 +/- 0.0016 from which the effective weak mixing angle is described: sin(2) theta(eff)(lept) = 0.23089 +/- 0.00089. The measurement of the leptonic width Gamma(ll) = 84.02 +/- 0.15 MeV leads to a determination of the effective rho parameter rho(eff)(lept) = 1.0064 +/- 0.0018. The data support the Standard Model and favour a light Higgs
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