223 research outputs found

    Search for Branons at LEP

    Get PDF
    We search, in the context of extra-dimension scenarios, for the possible existence of brane fluctuations, called branons. Events with a single photon or a single Z-boson and missing energy and momentum collected with the L3 detector in e^+ e^- collisions at centre-of-mass energies sqrt{s}=189-209$ GeV are analysed. No excess over the Standard Model expectations is found and a lower limit at 95% confidence level of 103 GeV is derived for the mass of branons, for a scenario with small brane tensions. Alternatively, under the assumption of a light branon, brane tensions below 180 GeV are excluded

    Search for Charginos with a Small Mass Difference with the Lightest Supersymmetric Particle at \sqrt{s} = 189 GeV

    Get PDF
    A search for charginos nearly mass-degenerate with the lightest supersymmetric particle is performed using the 176 pb^-1 of data collected at 189 GeV in 1998 with the L3 detector. Mass differences between the chargino and the lightest supersymmetric particle below 4 GeV are considered. The presence of a high transverse momentum photon is required to single out the signal from the photon-photon interaction background. No evidence for charginos is found and upper limits on the cross section for chargino pair production are set. For the first time, in the case of heavy scalar leptons, chargino mass limits are obtained for any \tilde{\chi}^{+-}_1 - \tilde{\chi}^0_1 mass difference

    Production of Single W Bosons at LEP

    Get PDF
    We report on the observation of single W boson production in a data sample collected by the L3 detector at LEP2. The signal consists of large missing energy final states with a single energetic lepton or two hadronic jets. The cross-section is measured to be 0.61−0.33+0.43±0.05  pb0.61^{+0.43}_{-0.33} \pm 0.05 \; \rm{pb} at the centre of mass energy \sqrt{s}=172 \GeV{}, consistent with the Standard Model expectation. From this measurement the following limits on the anomalous γ\gammaWW gauge couplings are derived at 95\% CL: −3.6Δκγ1.5\rm -3.6 \Delta \kappa_\gamma 1.5 and −3.6λγ3.6\rm -3.6 \lambda_\gamma 3.6

    Measurement of the Average Lifetime of b-Hadrons in Z Decays

    Get PDF
    We present a measurement of the average b-hadron lifetime τb{\rm \tau_b} at the e+e− \mathrm{e^+e^-} \, collider LEP. Using hadronic Z decays collected in the period from 1991 to 1994, two independent analyses have been performed. In the first one, the b-decay position is reconstructed as a secondary vertex of hadronic b-decay particles. The second analysis is an updated measurement of τb{\rm \tau_b} using the impact parameter of leptons with high momentum and high transverse momentum. The combined result is \begin{center} τb=[1549±9 (stat) ±15 (syst)]  fs {\rm \tau_b= [ 1549 \pm 9 \, (stat) \, \pm 15 \, (syst) ] \; fs \,} . \end{center} In addition, we measure the average charged b-decay multiplicity ⟨nb⟩{\rm \langle n_{\rm b}} \rangle and the normalized average b-energy ⟨xE⟩b{\rm \langle x_E \rangle_{\rm b}} at LEP to be \begin{center} ⟨nb⟩=4.90±0.04 (stat)±0.11 (syst){\rm \langle n_{\rm b} \rangle = 4.90 \pm 0.04 \ (stat) \pm 0.11 \, (syst)} , \end{center} \begin{center} ⟨xE⟩b=0.709±0.004 (stat+syst).{\rm \langle x_E \rangle_{\rm b} = 0.709 \pm 0.004 \, (stat + syst).} \end{center

    Juxtaposing BTE and ATE – on the role of the European insurance industry in funding civil litigation