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Measurement of the Z resonance parameters at LEP

Research output: Contribution to journalJournal article

Published

Journal publication date05/2000
JournalThe European Physical Journal C (EPJ C) - Particles and Fields
Journal number1
Volume14
Number of pages50
Pages1-50
Original languageEnglish

Abstract

The properties of the Z resonance are measured from the analysis of 4.5 million Z decays into fermion pairs collected with the Aleph detector at LEP. The data are consistent with lepton universality. The resonance parameters are measured to be MZ=(91.1885±0.0031)GeV/c2 , ΓZ=(2.4951±0.0043) GeV, σ0had=(41.559±0.058) nb and, combining the three lepton flavours, Rℓ=20.725±0.039 . The corresponding number of light neutrino species is Nν=2.983±0.013 and the strong coupling constant is αs(MZ)=0.114±0.004±0.002QCD+0.005log10[MH150GeV/c2] . The lepton pair forward-backward asymmetry is measured to be A0,ℓFB=0.0173±0.0016 from which the effective weak mixing angle is derived: sin2θlepteff=0.23089±0.00089 . The measurement of the leptonic width Γℓℓ=84.02±0.15 MeV leads to a determination of the effective ρ parameter ρlepteff=1.0064±0.0018 . The data support the Standard Model and favour a light Higgs.