Electroweak radiative corrections in Z-boson decays

Abstract

Contents. Introduction.New theories, new symmetries, new particles, new phenomena. W and Z boson 'factories'. What's the point of studying loop corrections?.2. Brief history of electroweak radiative corrections.Muon and neutron decays. Main relations of electroweak theory.Traditional parametrization of corrections to the µ-decay and the running α.Deep inelastic neutrino scattering by nucleons.Other processes involving neutral currents.3. On optimal parametrization of the theory and the choice of the Born approximation.Traditional choice of the main parameters.Optimal choice of the main parameters. Z boson decays. Amplitudes and widths.Asymmetries.The Born approximation for hadronless observables.4. One-loop corrections to hadronless observables. Four types of Feynman diagrams. Asymptotic limit at m 2 t ≫ m 2 Z . The functions V m (t, h), V A (t, h) and V R (t, h). The corrections δV i (t, h). Accidental (?) compensation and the mass of the t-quark. How to calculate V i ? 'Five steps'. Hadronic decays of the Z boson.The leading quarks and hadrons. Decays to pairs of light quarks. Decays to a pair b b. 6. Comparison of theoretical results with experimental data. LEPTOP code. General fit. 7. Conclusions. Achievements. Problems. Prospects.

Adler function from Re+e- (s) measurements: experiments vs QCD theory

“…It brought up the question of the possibility of finding the signal for the fifth quark in e + e − -annihilation. Moreover, an indirect determination of the mass of the sixth t-quark was made from detailed fits of the experimental data of the high-energy e + e −colliders LEP and SLC at the Z 0 -pole taking into account the effects of its virtual propagation (for a review see [ 6]). Impressively, the extracted mass of the t-quark turned out to be in agreement with the its direct "measurement", resulting from subsequent discovery of the 6th quark at the Tevatron.…”

Lepton Flavor Conserving Z Boson Decays and Scalar Unparticle

“…The present work is devoted to analysis whether the inclusion of the scalar unparticle effects overcomes the discrepancy of the BRs between the experimental and the QED corrected SM result (see [19] and references therein) for the lepton flavor conserving (LFC) Z decays. Furthermore, we study the new parameters arising with the unparticle effects and the dependencies of the BRs to these new parameters.…”