Precision Electroweak Measurements and Constraints on the Standard Model

This note presents constraints on Standard Model parameters using published and preliminary precision electroweak results measured at the electron-positron colliders LEP and SLC. The results are compared with precise electroweak measurements from other experiments, notably CDF and D{\O}at the Tevatron. Constraints on the input parameters of the Standard Model are derived from the combined set of results obtained in high-$Q^2$ interactions, and used to predict results in low-$Q^2$ experiments, such as atomic parity violation, M{\o}ller scattering, and neutrino-nucleon scattering. The main changes with respect to the experimental results presented in 2008 are new combinations of results on the W-boson mass and the mass of the top quark.Comment: 18 page

Z-Decays to b Quarks and the Higgs Boson Mass

A model independent analysis of the most recent averages of precision electroweak data from LEP and SLD finds a 3$\sigma$ deviation of the parameter $A_b$ from the Standard Model prediction. The fitted value of $m_H$ shows a strong dependence on the inclusion or exclusion of b quark data, and the Standard Model fits have poor confidence levels of a few percent when the latter are included. The good fits obtained to lepton data, c quark data and the directly measured top quark mass, give $m_t = 171.2_{-3.8}^{+3.7}$ GeV and indicate that the Higgs boson mass is most likely less than 200 GeV.Comment: 15 pages, 3 figures, 6 table

Higgs Searches at LEP

The four LEP experiments ALEPH, DELPHI, L3 and OPAL have performed decay-mode independent searches for scalar bosons, flavour-independent Higgs boson searches, searches for Higgs bosons in the Standard Model and several Two-Higgs-Doublet models and searches for doubly charged Higgs bosons at centre-of-mass energies up to 209 GeV. The results obtained and mostly combined by the LEP Higgs working group are discussed.Comment: submitted to the proceedings of the 37th Recontres de Moriond on Electroweak Interactions and Unified Theories, March 2002; 8 pages, 7 figures; minor wording changes, 2 figures replaced by b/w version, 1 reference adde