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    A Study of the reaction e+ e- ---> mu+ mu- around the Z0 pole

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    Measurements of the cross section and forward-backward asymmetry for the reaction e+e-→μ+μ- using the DELPHI detector at LEP are presented. The data come from a scan around the Z0 peak at seven centre of mass energies, giving a sample of 3858 events in the polar angle region 22° < θ < 158°. From a fit to the cross section for 43° < θ < 137°, a polar angle region for which the absolute efficiency has been determined, the square root of the product of the Z0→e+e- and Z0→μ+μ- partial widths is determined to be (ΓeΓμ)1/2 = 85.0 ± 0.9 (stat.) ± 0.8 (syst.) MeV. From this measurement of the partial width, the value of the effective weak mixing angle is determined to be sin2(θ̄w) = 0.2267 ± 0.0037. The ratio of the hadronic to muon pair partial widths is found to be Γh/Γμ = 19.89 ± 0.40 (stat.) ± 0.19 (syst.). The forward-backward asymmetry at the resonance peak energy ECMS = 91.22 GeV is found to be AFB = 0.028 ± 0.020 (stat.) ± 0.005 (syst.). From a combined fit to the cross section and forward-backward asymmetry data, the products of the electron and muon vector and axial-vector coupling constants are determined to be VeVμ = 0.0024 ± 0.0015 (stat.) ± 0.0004 (syst.) and AeAμ = 0.253 ± 0.003 (stat.) ± 0.003 (syst.). These results are in good agreement with the expectations of the minimal standard model
    Archivio della ricerca - Università degli studi di Napoli Federico II
    Oxford University Research Archive
    DSpace@NTUA (National Technical Univ. of Athens)
    DI-fusion
    ePubs: the open archive for STFC research publications
    Radboud Repository (Radboud Univ.)
    Archivio istituzionale della ricerca - Università di Genova
    CERN Document Server
    Archivio istituzionale della ricerca - Università di Padova

    Measurement of the τ lepton polarization in Z boson decays in proton-proton collisions at s s \sqrt{s} = 13 TeV

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    Abstract The polarization of τ leptons is measured using leptonic and hadronic τ lepton decays in Z → τ + τ − events in proton-proton collisions at s s \sqrt{s} = 13 TeV recorded by CMS at the CERN LHC with an integrated luminosity of 36.3 fb −1. The measured τ − lepton polarization at the Z boson mass pole is P τ Z Pτ(Z) {\mathcal{P}}_{\tau}\left(\textrm{Z}\right) = −0.144 ± 0.006 (stat) ± 0.014 (syst) = −0.144 ± 0.015, in good agreement with the measurement of the τ lepton asymmetry parameter of A τ = 0.1439 ± 0.0043 = − P τ Z −Pτ(Z) -{\mathcal{P}}_{\tau}\left(\textrm{Z}\right) at LEP. The τ lepton polarization depends on the ratio of the vector to axial-vector couplings of the τ leptons in the neutral current expression, and thus on the effective weak mixing angle sin2 θ W eff θWeff {\theta}_{\textrm{W}}^{\textrm{eff}} , independently of the Z boson production mechanism. The obtained value sin2 θ W eff θWeff {\theta}_{\textrm{W}}^{\textrm{eff}} = 0.2319 ± 0.0008(stat) ± 0.0018(syst) = 0.2319 ± 0.0019 is in good agreement with measurements at e + e − colliders
    SNU Open Repository and Archive
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    Archivio istituzionale della ricerca - Università di Bari
    Spiral - Imperial College Digital Repository
    Middle East Technical University Research Information System
    Helsingin yliopiston digitaalinen arkisto
    Archivio Istituzionale della Ricerca- Università del Piemonte Orientale
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    Archivio istituzionale della Ricerca - Scuola Normale Superiore
    Archivio della Ricerca - Università di Pisa
    Archivio istituzionale della ricerca - Alma Mater Studiorum Università di Bologna
    Archivio della ricerca- Università di Roma La Sapienza

    A Study of intermittency in hadronic Z0 decays

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    The correlations in rapidity in hadron production from e+e- annihilation near the Z0 resonance were studied by means of the method of factorial moments, using data taken with the DELPHI detector at LEP. The parton shower hadronization model was found to be in quantitative agreement with the data, in contrast with previous results at lower energies. © 1990.0SCOPUS: ar.jinfo:eu-repo/semantics/publishe
    Archivio della ricerca - Università degli studi di Napoli Federico II
    Archivio istituzionale della ricerca - Politecnico di Milano
    HAL-IN2P3
    Crossref
    Repositori d'Objectes Digitals per a l'Ensenyament la Recerca i la Cultura
    DSpace@NTUA (National Technical Univ. of Athens)
    DI-fusion
    ePubs: the open archive for STFC research publications
    Archivio istituzionale della ricerca - Università di Genova
    CERN Document Server
    Hal-Diderot
    Archivio istituzionale della ricerca - Università di Padova
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