A search for exotic unstable neutral and charged heavy leptons as well as for stable charged heavy leptons is performed with the L3 detector at LEP. Sequential, vector and mirror natures of heavy ...leptons are considered. No evidence for their existence is found and lower limits on their masses are set.
Doubly-charged Higgs bosons are searched for in e+e− collision data collected with the L3 detector at LEP at centre-of-mass energies up to 209 GeV. Final states with four leptons are analysed to tag ...the pair-production of doubly-charged Higgs bosons. No significant excess is found and lower limits at 95% confidence level on the doubly-charged Higgs boson mass are derived. They vary from 95.5 to 100.2 GeV, depending on the decay mode. Doubly-charged Higgs bosons which couple to electrons would modify the cross section and forward–backward asymmetry of the e+e−→e+e− process. The measurements of these quantities do not deviate from the Standard Model expectations and doubly-charged Higgs bosons with masses up to the order of a TeV are excluded.
The Double Chooz experiment presents an indication of reactor electron antineutrino disappearance consistent with neutrino oscillations. An observed-to-predicted ratio of events of ...0.944±0.016(stat)±0.040(syst) was obtained in 101 days of running at the Chooz nuclear power plant in France, with two 4.25GWth reactors. The results were obtained from a single 10m3 fiducial volume detector located 1050 m from the two reactor cores. The reactor antineutrino flux prediction used the Bugey4 flux measurement after correction for differences in core composition. The deficit can be interpreted as an indication of a nonzero value of the still unmeasured neutrino mixing parameter sin22θ13. Analyzing both the rate of the prompt positrons and their energy spectrum, we find sin22θ13=0.086±0.041(stat)±0.030(syst), or, at 90% C.L., 0.017
The ηπ+π− final state in two-photon collisions is studied with the L3 detector at LEP, at centre-of-mass energies from 183 to 209 GeV with an integrated luminosity of 664.6 pb−1. The f1(1285) meson ...is observed and the Q2 dependence of its production is compared to different form factor models. The γγ-coupling parameter Γγγ is found to be 3.5±0.6(stat.)±0.5(sys.) keV. The branching fraction Γ(f1(1285)→a0π)/Γ(f1(1285)→ηππ) is also measured.
The cross section of W-boson pair-production is measured with the L3 detector at LEP. In a data sample corresponding to a total luminosity of 629.4 pb−1, collected at centre-of-mass energies ranging ...from 189 to 209 GeV, 9834 four-fermion events with W bosons decaying into hadrons or leptons are selected. The total cross section is measured with a precision of 1.4% and agrees with the Standard Model expectation. Assuming charged-lepton universality, the branching fraction for hadronic W-boson decays is measured to be: Br(W→hadrons)=67.50±0.42(stat.)±0.30(syst.)%, in agreement with the Standard Model. Differential cross sections as a function of the W− production angle are also measured for the semi-leptonic channels qqeν and qqμν.
We report on a search for the first generation heavy neutrino that is an isosinglet under the standard SU(2)L gauge group. The data collected with the L3 detector at center-of-mass energies between ...130 GeV and 208 GeV are used. The decay channel Ne→eW is investigated and no evidence is found for a heavy neutrino, Ne, in a mass range between 80 GeV and 205 GeV. Upper limits on the mixing parameter between the heavy and light neutrino are derived.
Anomalous couplings of the Higgs boson are searched for through the processes e+e−→Hγ, e+e−→e+e−H and e+e−→HZ. The mass range 70 GeV<mH<190 GeV is explored using 602 pb−1 of integrated luminosity ...collected with the L3 detector at LEP at centre-of-mass energies s=189–209 GeV. The Higgs decay channels H→ff̄, H→γγ, H→Zγ and H→WW(∗) are considered and no evidence is found for anomalous Higgs production or decay. Limits on the anomalous couplings d, dB, Δg1Z, Δκγ and ξ2 are derived as well as limits on the H→γγ and H→Zγ decay rates.
A search, in e+e− collisions, for chargino, neutralino, scalar lepton and scalar quark pair-production is performed, without assuming R-parity conservation in decays, in the case that only one of the ...coupling constants λ or λ″ is non-negligible. No signal is found in data up to a centre-of-mass energy of 208 GeV. Limits on the production cross sections and on the masses of supersymmetric particles are derived.
Bose–Einstein correlations of both neutral and like-sign charged pion pairs are measured in a sample of 2 million hadronic Z decays collected with the L3 detector at LEP. The analysis is performed in ...the four-momentum difference range 300 MeV<Q<2 GeV. The radius of the neutral pion source is found to be smaller than that of charged pions. This result is in qualitative agreement with the string fragmentation model.
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