Precision electroweak measurements on the Z resonance

By The Aleph Collaboration, The Delphi Collaboration, the LHCf Collaboration, The Opal Collaboration, The Sld Collaboration, T. Group, the Sld electroweak, heavy flavour groups. 2005

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We report on the final electroweak measurements performed with data taken at the Z resonance by the experiments operating at the electron-positron colliders SLC and LEP. The data consist of 17 million Z decays accumulated by the ALEPH, DELPHI, L3 and OPAL experiments at LEP, and 600 thousand Z decays by the SLID experiment using a polarised beam at SLC. The measurements include cross-sections, forward-backward asymmetries and polarised asymmetries. The mass and width of the Z boson, m(Z) and Gamma(Z), and its couplings to fermions, for example the p parameter and the effective electroweak mixing angle for leptons, are precisely measured: m(Z) = 91.1875 +/- 0.0021 GeV, Gamma(Z) = 2.4952 +/- 0.0023 GeV, rho(l) = 1.0050 +/- 0.0010, sin(2)theta(eff)(lept) = 0.23153 +/- 0.00016. The number of light neutrino species is determined to be 2.9840 +/- 0.0082, in agreement with the three observed generations of fundamental fermions. The results are compared to the predictions of the Standard Model (SM). At the Z-pole, electroweak radiative corrections beyond the running of the QED and QCD coupling constants are observed with a significance of five standard deviations, and in agreement with the Standard Model. Of the many Z-pole measurements, the forward-backward asymmetry in b-quark production shows the largest difference with respect to its SM expectation, at the level of 2.8 standard deviations. Through radiative corrections evaluated in the framework of the Standard Model, the Z-pole data are also used to predict the mass of the top quark, m(t) = 173(+10)(+13) GeV, and the mass of the W boson, m(W) = 80.363 +/- 0.032 GeV. These indirect constraints are compared to the direct measurements, providing a stringent test of the SM. Using in addition the direct measurements of m(t) and m(W), the mass of the as yet unobserved SM Higgs boson is predicted with a relative uncertainty of about 50% and found to be less than 285 GeV at 95% confidence level. (c) 2006 Elsevier B.V. All rights reserved.

Subfields: Artificial Intelligence, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/4ac413cfdf37986ccfad8964544cd62a747ff03d

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Citations in the corpus

Naturalness and the Status of Supersymmetry (2013, methodology): “[89] ALEPH Collaboration, DELPHI Collaboration, L3 Collaboration, OPAL Collaboration, SLD Collaboration, LEP Electroweak Working Group, SLD Electroweak Group, SLD Heavy Flavour Group Collaboration, S.”
The Muon Magnetic Moment and Supersymmetry (2006, neutral): “The present experimental values are [114, 116]”
Higgs Boson studies at future particle colliders (2019, background): “f) At circular colliders, for Ab and Ac previous measurement uncertainties were dominated by the physics modelling [138] and the systematic uncertainty arising from this was only estimated by FCC-ee [135].”
B-physics anomalies: a guide to combined explanations (2017, background): “A modified Z coupling to τ -neutrino impacts the invisible Z decay reported as the number of neutrinos [73], Nν = 3+4δg Z νL = 2.”
Measurements of properties of the Higgs boson decaying into the four-lepton final state in pp collisions at s=13$$ \sqrt{s}=13 $$ TeV (2017, background): “[57] is 14% and the mutual compatibility between the three individual channels is 90%.”