[en] The characteristics of the L3 hadron calorimeter as realized in the observation of hadronic jets and other events from e⁺e^- c collisions at LEP are presented and discussed. The pattern-recognition algorithm utilizing the fine granularity of the calorimeter is described, and the observed overall resolution of 10.2% for hadron jets from Z decay is reported. The use of the calorimeter in providing information on muon energy losses is also noted. (orig.)

[en] We have searched for the pair produced charged Higgs particles in the decays of Z⁰ for the decay channels of H⁺H^-→τ⁺ντ^-anti ν, H⁺H^-→τνcs and H⁺H^-→canti santi cs. The data sample analyzed corresponds to approximately 50 000 hadronic decays of Z⁰. A lower limit of 36.5 GeV is obtained at the 95% confidence level for the mass of charged Higgs particle, independent of its decay branching ratio. (orig.)

[en] We have searched for excited taus from Z⁰ decay in the channels e⁺e^-→τ*⁺τ*^-→τ⁺τ^-γγ and e⁺e^-→ττ*→τ⁺τ^-γ, using the L3 detector at LEP. Using the τ* pair production channel, we can exclude a τ* up to a mass of 45.5 GeV at 95% confidence level. We have also determined upper limits on the ττ*Z⁰ and ττ*γ couplings as a function of m_τ* up to 89.3 GeV. (orig.)

[en] We have measured the cross-section of the reaction e⁺e^-→γγ at center of mass energies around the Z⁰ mass. The results are in good agreement with QED predictions. For the QED cutoff parameters the limit of Λ₊>103 GeV and Λ_->118 GeV are found. For the decays Z⁰→γγ, Z⁰→π⁰γ, Z⁰→ηγ and Z⁰→γγγ we find upper limits of 2.9x10^-4, 2.9x10^-4, 4.1x10^-4 and 1.2x10^-4, respectively. All limits are at 95% CL. (orig.)

[en] We have searched for the neutral Higgs boson produced in the decays of the Z⁰ through the process Z⁰→H⁰l⁺l^- in the mass range Msub(H⁰)<2 GeV. From the analysis of a data sample corresponding to about 70 000 Z⁰→hadrons we exclude a minimal standard model Higgs boson in the mass range 0< Msub(H⁰)<2 GeV at the 99% confidence level independent of the Higgs decay channels. (orig.)

[en] We describe the upgrade of the L3 detector for running at LHC. The principle goals are the precise measurement of electrons, photons and muons. (orig.)

[en] We have measured the partial widths for the three reactions e⁺e^-→Z⁰→e⁺e^-, μ⁺μ^-, τ⁺τ^-. The results are Γ_ee=84.3±1.3 MeV, √Γ_eeΓ_μμ=83.3±1.3 MeV, and √Γ_eeΓ_ττ=83.9±1.4 MeV, where the errors are statistical. The systematic errors are estimated to be 1.0 MeV, 0.9 MeV, and 1.4 MeV, respectively. We perform a simultaneous fit to the cross sections for the e⁺e^-→e⁺e^-, μ⁺μ^-, and τ⁺τ^- data, the differential cross section as a function of polar angle for the electron data, and the forward-backward asymmetry for the muon data. We obtain the leptonic partial with Γ_ll=84.0±0.9(stat). MeV. The systematic error is estimated to be 0.8 MeV. Also, we obtain the axial-vector and vector weak coupling constants of charged leptons, g_A=-0.500±0.003 and g_V=-0.064_-0.013^+0.017. (orig.)