Results from the L3 experiments at LEP

Abstract

In this report we summarize the major results from the first three years of running of the L3 detector at the Large Electron Positron collider (LEP). The L3 detector was designed to measure electrons, photons and muons with high precision; it has achieved (ΔE/E0 ≃ 1.4% for electrons and photons at E = 45 GeV and (Δp/p) ≃ 2.5% for muons at p = 45 GeV. Most of the experimental results presented are based on approximately 500 000 Z events. The data provide foue independent checks of the Standard Model weak neutral currents to an accuracy of ≃ 1%. These are: the measurement of Z parameters; the measurement of the forward-backward charge asymmetry of ;epton pairs; the measurement of asymmetry parameters from Z→bb̄ decays; and the measurement of the gp lepton polarization asymmetry. The data also information on weak charged currents from measurements of b hadrons such as decay width, lifetime, and B⁰-B⁰ mixing, and from measurements of τ leptons such as their lifetime and branching ratios.The large number of Z events and the resoltuion of the L3 detector allow presicion tests of QED and QCD, including the production of π⁰, η and hard photons.Leptonic final states with hard isolated photons are analyzed and high mass photon pairs are observed. Higgs boson production has not been observed and limits are given in the context of the standard Model and its supersymmetric extensions. We also present upper limits on rare Z decays such as Z → γγγ and on flavor violating decays such as Z → τ, μτ. Finally, upper limits obtained in the search for various new particles and new interactions are reported.