Cécile Lachaud

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Construction of the first stage of the Pierre Auger Observatory has begun. The aim of the Observatory is to collect unprecedented information about cosmic rays above 10 eV: The first phase of the project, the construction and operation of a prototype system, known as the engineering array, has now been completed. It has allowed all of the sub-systems that(More)
Using data collected at the Pierre Auger Observatory during the past 3.7 years, we demonstrated a correlation between the arrival directions of cosmic rays with energy above 6 x 10(19) electron volts and the positions of active galactic nuclei (AGN) lying within approximately 75 megaparsecs. We rejected the hypothesis of an isotropic distribution of these(More)
The surface detector array of the Pierre Auger Observatory is sensitive to Earth-skimming tau neutrinos that interact in Earth's crust. Tau leptons from nu(tau) charged-current interactions can emerge and decay in the atmosphere to produce a nearly horizontal shower with a significant electromagnetic component. The data collected between 1 January 2004 and(More)
The energy spectrum of cosmic rays above 2.5 x 10;{18} eV, derived from 20,000 events recorded at the Pierre Auger Observatory, is described. The spectral index gamma of the particle flux, J proportional, variantE;{-gamma}, at energies between 4 x 10;{18} eV and 4 x 10;{19} eV is 2.69+/-0.02(stat)+/-0.06(syst), steepening to 4.2+/-0.4(stat)+/-0.06(syst) at(More)
We describe the measurement of the depth of maximum, X{max}, of the longitudinal development of air showers induced by cosmic rays. Almost 4000 events above 10;{18} eV observed by the fluorescence detector of the Pierre Auger Observatory in coincidence with at least one surface detector station are selected for the analysis. The average shower maximum was(More)
The cosmic ray spectrum has been shown to extend well beyond 10eV. With nearly 20 events observed in the last 40 years, it is now established that particles are accelerated or produced in the universe with energies near 10eV. In all production models neutrinos and photons are part of the cosmic ray flux. In acceleration models (bottom-up models), they are(More)
P. Astier n, D. Autiero h, A. Baldisseri r, M. Baldo-Ceolin m, M. Banner n, G. Bassompierre a, K. Benslama i, N. Besson r, I. Bird h,i, B. Blumenfeld b, F. Bobisut m, J. Bouchez r, S. Boyd t, A. Bueno c,x, S. Bunyatov f, L. Camilleri h, A. Cardini j, P.W. Cattaneo o, V. Cavasinni p, A. Cervera-Villanueva h,v, G. Collazuol m, G. Conforto h,u,1, C. Conta o,(More)
We report on a search for heavy neutrinos (ν4) produced in the decay Ds → τν4 at the SPS proton target followed by the decay ν4 → ντe +e− in the NOMAD detector. Both decays are expected to occur if ν4 is a component of ντ . From the analysis of the data collected during the 1996-1998 runs with 4.1 × 1019 protons on target, a single candidate event(More)
We present our new measurement of the cross-section for charm dimuon production in neutrino-iron interactions based upon the full statistics collected by the NOMAD experiment. After background subtraction we observe 15,344 charm dimuon events, providing the largest sample currently available. The analysis exploits the large inclusive charged current sample(More)
We carried out a model-independent search for light scalar or pseudoscalar particles a’s (an example of which is the axion) that couple to two photons by using a photon-regeneration method at high energies allowing a substantial increase in the sensitivity to eV masses. The experimental set-up is based on elements of the CERN West Area Neutrino Facility(More)