121 research outputs found

    A search for flaring very-high-energy cosmic gamma-ray sources with the L3+C muon spectrometer

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    The L3+C muon detector at the CERN electron-positron collider, LEP, is used for the detection of very-high-energy cosmic gamma-ray sources through the observation of muons of energies above 20, 30, 50 and 100 GeV. Daily or monthly excesses in the rate of single-muon events pointing to some particular direction in the sky are searched for. The periods from mid July to November 1999, and April to November 2000 are considered. Special attention is also given to a selection of known gamma-ray sources. No statistically significant excess is observed for any direction or any particular source. (c) 2006 Elsevier B.V. All rights reserved

    The solar flare of the 14th of July 2000 (L3+C detector results)

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    Aims. Several experiments have reported observations on possible correlations between the flux of high energy muons and intense solar flares. If confirmed, these observations would have significant implications for acceleration processes in the heliosphere able to accelerate protons and other ions to energies of at least tens of GeV. Methods. The solar flare of the 14 of July 2000 offered a unique opportunity for the L3+C experiment to search for a correlated enhancement in the flux of muons using the L3 precision muon spectrometer. Its capabilities for observing a directional excess in the flux of muons above 15 GeV (corresponding to primary proton energies above 40 GeV) are presented along with observations made on the 14th of July 2000. Results. We report an excess which appeared at a time coincident with the peak increase of solar protons observed at lower energies. The probability that the excess is a background fluctuation is estimated to be 1 %. No similar excess of the muon flux was observed up to 1.5 h after the solar flare time. © ESO 2006

    A search for flaring very-high-energy cosmic gamma-ray sources with the L3+C muon spectrometer

    No full text
    The L3+C muon detector at the CERN electron-positron collider, LEP, is used for the detection of very-high-energy cosmic gamma-ray sources through the observation of muons of energies above 20, 30, 50 and 100 GeV. Daily or monthly excesses in the rate of single-muon events pointing to some particular direction in the sky are searched for. The periods from mid July to November 1999, and April to November 2000 are considered. Special attention is also given to a selection of known gamma-ray sources. No statistically significant excess is observed for any direction or any particular source. (c) 2006 Elsevier B.V. All rights reserved.LPH

    Measurement of the running of the electromagnetic coupling at large momentum-transfer at LEP

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    The evolution of the electromagnetic coupling, alpha, in the momentum-transfer range 1800 GeV2 \u3c -Q(2) \u3c 21600 GeV2 is studied with about 40 000 Bhabha-scattering events collected with the L3 detector at LEP at centre-of-mass energies root s = 189-209 GeV. The running of a is parametrised as: alpha(Q(2)) = (1-C Delta alpha(Q2))/(alpha 0) where alpha(0) = alpha(Q(2) = 0) is the fine-structure constant and C = 1 corresponds to the evolution expected in QED. A fit to the differential cross section of the e(+)e(-) -\u3e e(+)e(-) process for scattering angles in the range vertical bar cos theta vertical bar \u3c 0.9 excludes the hypothesis of a constant value of alpha, C = 0, and validates the QED prediction with the result: C = 1.05 +/- 0.07 +/- 0.14, where the first uncertainty is statistical and the second systematic. (c) 2005 Elsevier B.V. All rights reserved

    A search for flaring very-high-energy cosmic gamma-ray sources with the L3+C muon spectrometer RID C-2983-2009 RID C-4549-2008 RID C-5719-2008

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    Measurement of triple-gauge-boson couplings of the W boson at LEP RID C-2983-2009 RID C-4549-2008 RID C-5719-2008

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    Search for an invisibly-decaying Higgs boson at LEP RID C-2983-2009 RID C-4549-2008 RID C-5719-2008

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    Compton scattering of quasi-real virtual photons at LEP RID C-2983-2009 RID C-4549-2008 RID C-5719-2008

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    Total cross section in gamma gamma collisions at LEP RID C-2983-2009 RID C-4549-2008 RID C-5719-2008

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