189 research outputs found

    Search for the standard model Higgs boson at LEP

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    Создание программного обеспечения для проектирования и расчета ректификационных колонн

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    В работе описаны разработанные и программно реализованные методики и алгоритмы расчета технологических и конструкционных параметров тарельчатых и насадочных ректификационных колонн для разделения двух, многокомпонентных и изотопных смесей. Представлены результаты их верификации. Показана хорошая сходимость результатов расчета с известными литературными данными.This work describes the developed and software implemented methods and algorithms for calculating the technological and design parameters of disc-shaped and packed distillation columns for separating two, multicomponent and isotopic mixtures. The results of the verification of the methods are presented. A good convergence of the calculation results with the known literature data is shown

    Внедрение и принцип работы системы сейсмического мониторинга горного массива для работы в условиях ООО "Шахта "Усковская"

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    The status of the Silicon Microvertex Detector (SMD) and its installation into the LEP-L3 experiment are presented, highlighting novel features and sophisticated techniques. Preliminary results based on 1993 data are given and compared with Monte Carlo predictions, to understand the detector performances and its tracking capabilities

    Determination of the number of light neutrino species from single photon production at LEP

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    A determination of the number of light neutrino families performed by measuring the cross section of single photon production in \ee\ collision near the \Zo\ resonance is reported. From an integrated luminosity of 100 pb1100~\mathrm{pb^{-1}}, collected during the years 1991--94, we have observed 2091 single photon candidates with an energy above 1~\GeV\ in the polar angular region 45<θγ<13545^\circ < \theta_\gamma < 135^\circ. From a maximum likelihood fit to the single photon cross section, the \Zo\ decay width into invisible particles is measured to be \Ginv = 498 \pm 12 \mathrm{(stat)} \pm 12 \mathrm{(sys)~MeV}. Using the Standard Model couplings of neutrinos to the \Zo, the number of light neutrino species is determined to be $N_\nu = 2.98 \pm 0.07 (\mathrm{stat}) \pm 0.07 (\mathrm{sys}).

    Search for R-Parity Breaking Sneutrino Exchange at LEP

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    We report on a search for R--parity breaking effects due to supersymmetric tau--sneutrino exchange in the reactions e+e- to e+e- and e+e- to mu+mu- at centre--of--mass energies from 91~{\GeV} to 172~{\GeV}, using the L3 detector at LEP. No evidence for deviations from the Standard Model expectations of the measured cross sections and forward--backward asymmetries for these reactions is found. Upper limits for the couplings λ131\lambda_{131} and λ232\lambda_{232} for sneutrino masses up to m_{\SNT} \leq 190~\GeV are determined from an analysis of the expected effects due to tau sneutrino exchange

    Search for charged Higgs bosons in e+ee^+ e^- collisions at centre-of-mass energies between 130 and 183 GeV

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    A search for pair-produced charged Higgs bosons is performed with the L3 detector at LEP using data collected at centre-of-mass energies from \mbox{130 to 183 \GeV{}}, corresponding to an integrated luminosity of 88.3 \pb. The Higgs decays into a charm and a strange quark or into a tau lepton and its associated neutrino are considered. The observed candidates are consistent with the expectations from Standard Model background processes. A lower limit of 57.5 \GeV{} on the charged Higgs mass is derived at 95\% CL, independent of the decay branching ratio \mathrm{Br(H^\pm\ra \tau\nu)}

    Search for new physics phenomena in fermion-pair production at LEP

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    The measurements of hadron and lepton--pair production cross sections and lepton--pair forward--backward asymmetries performed with the L3 detector at centre--of--mass energies between 130 GeV and 172 GeV are used to search for new physics phenomena. New physics effects involving four fermion vertices -- contact interactions -- are looked for in all channels. For hadron production the exchange of virtual leptoquarks and scalar quarks is studied. No evidence for deviations from the Standard Model expectations is found. Lower limits on the scale Λ\Lambda of contact interactions in the range 1.2 -- 7.1 TeV are obtained at the 95\% confidence level for various models. Upper limits on the coupling strengths of leptoquarks and scalar quarks are derived

    Measurement of the inclusive charmless semileptonic branching fraction of beauty hadrons and a determination of |VubV_{ub}| at LEP

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    A measurement of the inclusive charmless semileptonic branching fraction of beauty hadrons, bXuν\mathrm{b}\rightarrow\mathrm{X}_\mathrm{u }\ell\nu, has been performed using almost two million hadronic Z decays collected by the L3 experiment at LEP, yielding the result: \begin{displaymath} \mathrm{Br}(\mathrm{b}\rightarrow\mathrm{X}_\mathr m{u}\ell\nu) = (3.3 \pm 1.0 \pm 1.7)\times 10^{-3}. \end{displaymath} The first uncertainty is statistical and the second is systematic. The modulus of the Cabibbo-Kobayashi-Maskawa matrix element Vub\mathrm{V_{ub}} extracted from this measurement is: \begin{displaymath} |\mathrm{V_{ub}}| = (6.0\, ^{+0.8}_{-1.0} \, ^{+1.4}_{-1.9} \pm 0.2)\times 10^{-3}, \end{displaymath} where the uncertainties are statistical, systematic and theoretical, respectively

    Heavy Quarkonium Production in Z Decays

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    We report measurements of the inclusive production of heavy quarkonium states in Z\mathrm {Z} decays based on the analysis of 3.6 million hadronic events collected by the L3 detector at LEP. The measurement of inclusive J production and an improved 95%95\% confidence level upper limit on Υ\Upsilon production are presented. In addition, two independent measurements of the ratio, fpf_{\mathrm{p}}, of prompt J mesons to those from B decay are made using two different isolation cuts to separate prompt J mesons from J mesons produced in the decays of b hadrons. The results are: % \begin{eqnarray} \mathrm{Br}(\mathrm{Z} \rightarrow \mathrm{J} + \mathrm{X}) & = & (3.21 \pm 0.21 \; \mathrm{(stat.)} \; ^{+ 0.19}_{- 0.28} \; \mathrm{(sys.)} ) \times 10^{-3} \; , \nonumber \\ \mathrm{Br}(\mathrm {Z} \rightarrow \Upsilon(\mathrm{1S} + X) & < & 4.4 \times 10^{-5} \; , \nonumber \\ %% f_{\mathrm{p}} & = & (7.1 \pm 2.1 \; \mathrm{(stat.)} \; \pm 1.2 \; \mathrm{(sys.)} \; ^{+1.5}_{-0.8} \;\mathrm{(theo.)} ) \times 10^{-2} \; . \nonumbe
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