A combined analysis of the hadronic and leptonic decays of the Z0

Abstract

Abstract We report on a measurement of the mass of the Z 0 boson, its total width, and its partial decay widths into hadrons and leptons. On the basis of 25 801 hadronic decays and 1999 decays into electrons, muons or taus, selected over eleven energy points between 88.28 GeV and 95.04 GeV, we obtain from a combined fit to hadrons and leptons a mass of M z = 91.154 ± 0.021 (exp) ± 0.030 (LEP) GeV, and a total width of Γ z = 2.536 ± 0.045 GeV. The errors on M z have been separated into the experimental error and the uncertainty due to the LEP beam energy. The measured leptonic partial widths are Γ ee = 81.2 ± 2.6 MeV, Γ μμ = 82.6 ± 5.8 MeV, and Γ ττ = 85.7 ± 7.1 MeV, consistent with lepton universality. From a fit assuming lepton universality we obtain Γ l + l − = 81.9 ± 2.0 MeV. The hadronic partial width is Γ had = 1838 ± 46 MeV. From the measured total and partial widths a model independent value for the invisible width is calculated to be Γ inv = 453 ± 44 MeV. The errors quoted include both the statistical and the systematic uncertainties.