Search results for "Method"
showing 10 items of 13253 documents
Limit on the diffuse flux of ultrahigh energy tau neutrinos with the surface detector of the Pierre Auger Observatory
2009
Data collected at the Pierre Auger Observatory are used to establish an upper limit on the diffuse flux of tau neutrinos in the cosmic radiation. Earth-skimming ντ may interact in the Earth's crust and produce a τ lepton by means of charged-current interactions. The τ lepton may emerge from the Earth and decay in the atmosphere to produce a nearly horizontal shower with a typical signature, a persistent electromagnetic component even at very large atmospheric depths. The search procedure to select events induced by τ decays against the background of normal showers induced by cosmic rays is described. The method used to compute the exposure for a detector continuously growing with time is de…
Anisotropy and chemical composition of ultra-high energy cosmic rays using arrival directions measured by the Pierre Auger Observatory
2011
The Pierre Auger Collaboration has reported evidence for anisotropy in the distribution of arrival directions of the cosmic rays with energies $E>E_{th}=5.5\times 10^{19}$ eV. These show a correlation with the distribution of nearby extragalactic objects, including an apparent excess around the direction of Centaurus A. If the particles responsible for these excesses at $E>E_{th}$ are heavy nuclei with charge $Z$, the proton component of the sources should lead to excesses in the same regions at energies $E/Z$. We here report the lack of anisotropies in these directions at energies above $E_{th}/Z$ (for illustrative values of $Z=6,\ 13,\ 26$). If the anisotropies above $E_{th}$ are du…
Strategic analysis of transit service quality using fuzzy AHP methodology
2013
Customer satisfaction analyses are deeply based on customers' judgments and as consequence, they can be characterized by a certain degree of uncertainty generally ascribed to coexistence of three relevant aspects: vagueness, imprecision and subjectivity. In the present paper, a methodology able to handle such uncertainty, based on the ServQual discrepancy paradigm and that uses in combined manner the AHP method and the Fuzzy Sets Theory is proposed in order to overcome limitations of the traditional service evaluation approaches. Subsequently, by considering the Italian public transit service sector, a service quality analysis is conducted and the overall transit service quality structure i…
Updated measurement of the τ lepton lifetime
1997
A new measurement of the mean lifetime of the tau lepton is presented. Three different analysis methods are applied to a sample of 90000 tau pairs, collected in 1993 and 1994 with the ALEPH detector at LEP. The average of this measurement and those previously published by ALEPH is tau_tau = 290.1 +- 1.5 +- 1.1 fs.
The IceCube data acquisition system: Signal capture, digitization, and timestamping
2008
IceCube is a km-scale neutrino observatory under construction at the South Pole with sensors both in the deep ice (InIce) and on the surface (IceTop). The sensors, called Digital Optical Modules (DOMs), detect, digitize and timestamp the signals from optical Cherenkov-radiation photons. The DOM Main Board (MB) data acquisition subsystem is connected to the central DAQ in the IceCube Laboratory (ICL) by a single twisted copper wire-pair and transmits packetized data on demand. Time calibration is maintained throughout the array by regular transmission to the DOMs of precisely timed analog signals, synchronized to a central GPS-disciplined clock. The design goals and consequent features, func…
Search for Extraterrestrial Point Sources of Neutrinos with AMANDA-II
2003
We present the results of a search for point sources of high energy neutrinos in the northern hemisphere using AMANDA-II data collected in the year 2000. Included are flux limits on several AGN blazars, microquasars, magnetars and other candidate neutrino sources. A search for excesses above a random background of cosmic-ray-induced atmospheric neutrinos and misreconstructed downgoing cosmic-ray muons reveals no statistically significant neutrino point sources. We show that AMANDA-II has achieved the sensitivity required to probe known TeV gamma-ray sources such as the blazar Markarian 501 in its 1997 flaring state at a level where neutrino and gamma-ray fluxes are equal.
Côté mauvaises herbes, tir de barrage sur trois envahissantes
2006
National audience; Les plantes envahissantes sont évoquées à la conférence sur les zones non agricoles de l'AFPPà Avignon les 11 et 12octobre 2006. La situation à leur égard en France et en Europe est présentée, notamment les dispositions réglementaires et l'identité des 34 principales espèces. Deux communications traitent de l'ambroisie à feuille d'armoise Ambrosia artemisiifolia. Un point sur les méthodes de lutte mécanique, chimique, etc.) insiste sur l'intérêt de la prévention (enherbement, etc.)et de la concertation entre acteurs agricoles et non agricoles. Des essais de lutte chimique (glyphosate ou glufosinate-ammonium en 2004 et 2005, les montrent équivalents et intéressants en débu…
Monte Carlo simulations of the solid-liquid transition in hard spheres and colloid-polymer mixtures
2010
Monte Carlo simulations at constant pressure are performed to study coexistence and interfacial properties of the liquid-solid transition in hard spheres and in colloid-polymer mixtures. The latter system is described as a one-component Asakura-Oosawa (AO) model where the polymer's degrees of freedom are incorporated via an attractive part in the effective potential for the colloid-colloid interactions. For the considered AO model, the polymer reservoir packing fraction is eta_p^r=0.1 and the colloid-polymer size ratio is q=sigma_p/\sigma=0.15 (with sigma_p and sigma the diameter of polymers and colloids, respectively). Inhomogeneous solid-liquid systems are prepared by placing the solid fc…
Search for high energy cosmic muon neutrinos from variable gamma-ray sources and time calibration of the optical modules of the ANTARES telescope
2015
325 páginas. Tesis Doctoral del Departamento de Física Atómica, Molecular y Nuclear de la Universidad de Valencia y del Instituto de Física Corpuscular (IFIC).
Comparison of 3 ionisation methods - electron ionisation, chemical ionisation and atmospheric pressure photoionisation - for the characterisation of …
2021
International audience; Gas chromatography (GC) is a reproducible, robust, selective and sensitive method to analyse volatile organic compounds (VOCs) in a wide range of applications. The separated analytes are generally characterised by mass spectrometry (MS) under vacuum conditions. The main ionisation method is the Electron Ionisation (EI): high energy exchanges occur, causing reproducible molecular fragmentations. Chemical Ionisation (CI) is another ionisation method where a reactive gas (i.e. methane or ammonia) is ionised to form reactant ions. GC-MS can also be conducted under atmospheric pressure. Atmospheric Pressure PhotoIonisation (APPI) is the most recent source [1]. Emitted pho…