Mass limits for excited electrons and muons from Z\u3csup\u3e0\u3c/sup\u3e decay

\u3cp\u3eWe searched for excited electrons and muons from Z\u3csup\u3e0\u3c/sup\u3e decay in the channels ee→eeγ, ee→eeγγ, ee→(e)eγ, ee→μμγ, ee→μμγγ. using the L3 detector at LEP. The lower mass limit for e\u3csup\u3e*\u3c/sup\u3e is 45.0 GeV and for μ\u3csup\u3e*\u3c/sup\u3e 45.3 GeV. The upper limits of ℓℓ\u3csup\u3e*\u3c/sup\u3eZ\u3csup\u3e0\u3c/sup\u3e and ℓℓ\u3csup\u3e*\u3c/sup\u3eγ couplings at 95% CL have been determined up to m\u3csub\u3eℓ*\u3c/sub\u3e close to the Z\u3csup\u3e0\u3c/sup\u3e mass.\u3c/p\u3

Determination of α\u3csub\u3es\u3c/sub\u3e from jet multiplicities measured on the Z\u3csup\u3e0\u3c/sup\u3e resonance

\u3cp\u3eWe present a study of jet multiplicities based on 37 000 hadronic Z\u3csup\u3e0\u3c/sup\u3e boson decays. From this data we determine the strong coupling constant α\u3csub\u3es\u3c/sub\u3e=0.115±0.005 (exp.)\u3csub\u3e-0.010\u3c/sub\u3e\u3csup\u3e+0.012\u3c/sup\u3e (theor.) to second order QCD at √s=91.22GeV.\u3c/p\u3

A determination of electroweak parameters from Z\u3csup\u3e0\u3c/sup\u3e→μ\u3csup\u3e+\u3c/sup\u3eμ\u3csup\u3e-\u3c/sup\u3e (γ)

\u3cp\u3eWe have measured the partial width and forward-backward charge asymmetry for the reaction e\u3csup\u3e+\u3c/sup\u3ee\u3csup\u3e-\u3c/sup\u3e→Z\u3csup\u3e0\u3c/sup\u3e→μ\u3csup\u3e+\u3c/sup\u3eμ \u3csup\u3e-\u3c/sup\u3e(γ). We obtain a partial width Γ\u3csub\u3eμμ\u3c/sub\u3e of 83.3±1.3(stat)±0.9(sys) MeV and the following values for the vector and axial vector couplings: g\u3csub\u3ev\u3c/sub\u3e=-0.062\u3csub\u3e-0.015\u3c/sub\u3e \u3csup\u3e+0.020\u3c/sup\u3e and g\u3csub\u3eA\u3c/sub\u3e=-0.497\u3csub\u3e-0.005\u3c/sub\u3e \u3csup\u3e+0.005\u3c/sup\u3e. From our measurement of the partial width and the mass of the Z\u3csup\u3e0\u3c/sup\u3e boson we determine the effective electroweak mixing angle, sin\u3csup\u3e2\u3c/sup\u3eθ\u3csub\u3ew\u3c/sub\u3e=0.232±0.005, and the neutral current coupling strength parameter, ρ{variant}=0.998±0.016.\u3c/p\u3

Search for a low mass neutral Higgs boson in Z\u3csup\u3e0\u3c/sup\u3e decay

\u3cp\u3eWe have searched for the neutral Higgs boson produced in the decays of the Z\u3csup\u3e0\u3c/sup\u3e through the process Z\u3csup\u3e0\u3c/sup\u3e → H\u3csup\u3e0\u3c/sup\u3el\u3csup\u3e+\u3c/sup\u3el\u3csup\u3e-\u3c/sup\u3e in the mass range M\u3csub\u3eH\u3csup\u3e0\u3c/sup\u3e \u3c/sub\u3e <2 GeV. From the analysis of a data sample corresponding to about 70 000 Z\u3csup\u3e0\u3c/sup\u3e→ hadrons we exclude a minimal standard model Higgs boson in the mass range 0<M\u3csub\u3eH\u3csup\u3e0\u3c/sup\u3e \u3c/sub\u3e<2 GeV at the 99% confidence level independent of the Higgs decay channels.\u3c/p\u3

A test of QCD based on 4-jet events from Z\u3csup\u3e0\u3c/sup\u3e decays

\u3cp\u3eWe present a study of 4200 4-jet events from Z\u3csup\u3e0\u3c/sup\u3e boson decays. The measured angular correlations between jets are reproduced well by QCD. An alternative abelian model fails to describe the data.\u3c/p\u3

Search for the charged Higgs boson in Z\u3csup\u3e0\u3c/sup\u3e decay

\u3cp\u3eWe have searched for the pair produced charged Higgs particles in the decays of Z\u3csup\u3e0\u3c/sup\u3e for the decay channels of H\u3csup\u3e+\u3c/sup\u3eH\u3csup\u3e-\u3c/sup\u3e→τ\u3csup\u3e+\u3c/sup\u3eντ\u3csup\u3e-\u3c/sup\u3e ν, H\u3csup\u3e+\u3c/sup\u3eH\u3csup\u3e-\u3c/sup\u3e→τνcs and H\u3csup\u3e+\u3c/sup\u3eH\u3csup\u3e-\u3c/sup\u3e→cscs. The data sample analyzed corresponds to approximately 50 000 hadronic decays of Z\u3csup\u3e0\u3c/sup\u3e. 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.\u3c/p\u3

Search for excited taus from Z\u3csup\u3e0\u3c/sup\u3e decays

\u3cp\u3eWe have searched for excited taus from Z\u3csup\u3e0\u3c/sup\u3e decay in the channels e\u3csup\u3e+\u3c/sup\u3ee\u3csup\u3e-\u3c/sup\u3e → τ\u3csup\u3e*+\u3c/sup\u3eτ\u3csup\u3e*-\u3c/sup\u3e → τ\u3csup\u3e+\u3c/sup\u3eτ\u3csup\u3e-\u3c/sup\u3eγ γ and e\u3csup\u3e+\u3c/sup\u3ee\u3csup\u3e-\u3c/sup\u3e → ττ\u3csup\u3e*\u3c/sup\u3e → τ\u3csup\u3e+\u3c/sup\u3eτ\u3csup\u3e-\u3c/sup\u3eγ, using the L3 detector at LEP. Using the τ\u3csup\u3e*\u3c/sup\u3e pair production channel, we can exclude a τ\u3csup\u3e*\u3c/sup\u3e up to a mass of 45.5 geV at 95% confidence level. We have also determined upper limits on the ττ\u3csup\u3e*\u3c/sup\u3eZ\u3csup\u3e0\u3c/sup\u3e and ττ\u3csup\u3e*\u3c/sup\u3eγ couplings as a function of m\u3csub\u3eτ*\u3c/sub\u3e up to 89.3 GeV.\u3c/p\u3

Search for excited neutrinos from Z\u3csup\u3e0\u3c/sup\u3e decays

\u3cp\u3eWe have searched for the excited electron neutrino produced from Z\u3csup\u3e0\u3c/sup\u3e decays in the channel e\u3csup\u3e+\u3c/sup\u3ee\u3csup\u3e-\u3c/sup\u3e→νν\u3csup\u3e*\u3c/sup\u3e using the L3 detector at LEP. The decays ν\u3csup\u3e*\u3c/sup\u3e→eW and ν\u3csup\u3e*\u3c/sup\u3e→νγ have been investigated. We have determined an upper limit on the Zνν\u3csup\u3e*\u3c/sup\u3e coupling as a function of m\u3csub\u3eν\u3csup\u3e*\u3c/sup\u3e\u3c/sub\u3e up to the Z\u3csup\u3e0\u3c/sup\u3e mass.\u3c/p\u3

Search for the neutral Higgs bosons of the minimal supersymmetric standard model from Z\u3csup\u3e0\u3c/sup\u3e decays

\u3cp\u3eWe present the results from a search for the light neutral scalar Higgs boson h° and the pseudoscalar Higgs boson A° of the minimal super-symmetric standard model. The analysis is based on a data sample corresponding to 71 000 hadronic Z° decays recorded with the L3 detector at LEP. No evidence for the existence of the neutral Higgs bosons h° and A° has been found. The region of h° and A° masses up to 41.5 GeV is excluded at 95% confidence level.\u3c/p\u3