291 research outputs found

    Long-Baseline Neutrino Facility (LBNF) and Deep Underground Neutrino Experiment (DUNE) Conceptual Design Report Volume 2: The Physics Program for DUNE at LBNF

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    The Physics Program for the Deep Underground Neutrino Experiment (DUNE) at the Fermilab Long-Baseline Neutrino Facility (LBNF) is described

    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

    Local multiplicity fluctuations in hadronic Z decay

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    Local multiplicity fluctuations in hadronic Z decays are studied using the L3 detector at LEP. Bunching parameters are used for the first time in addition to the normalised factorial moment method. The bunching parameters directly demonstrate that the fluctuations in rapidity are multifractal. Monte Carlo models show overall agreement with the data, reproducing the trend, although not always the magnitude, of the factorial moments and bunching parameters

    Angular multiplicity fluctuations in hadronic Z decays and comparison to QCD models and analytical calculations

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    Local multiplicity fluctuations in angular phase space intervals are studied using factorial moments measured in hadronic events at \sqrt{s}\simeq 91.2\GeV, which were collected by the L3 detector at LEP in 1994. Parton shower Monte Carlo programs agree well with the data. On the other hand, first-order QCD calculations in the Double Leading Log Approximation and the Modified Leading Log Approximation are found to deviate significantly from the data

    Measurement of η(958)\eta '(958) formation in two-photon collisions at LEP1

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    The formation of the eta' in the reaction ee->ee eta'->ee pi pi gamma has been measured by the L3 detector at a centre-of-mass energy of 91 GeV. The radiative width of the eta' has been found to be 4.17 +/- 0.10(stat.) +/- 0.27(sys.) keV . The Q^2 dependence of the eta' formation cross section has been measured for Q^2 < 10 GeV^2 and the eta' electromagnetic transition form factor has been determined. The form factor can be parametrised by a pole form with Lambda = 0.900 +/- 0.046(stat) +/- 0.022(sys) GeV. It is also consistent with recent non-perturbative QCD calculations
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