Publications (92)201.46 Total impact
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Dataset: Ave et al Precis measur fluo AP2013
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Article: Precise measurement of the absolute fluorescence yield of the 337 nm band in atmospheric ga-ses
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ABSTRACT: A measurement of the absolute fluorescence yield of the 337 nm nitrogen band, relevant to ultra-high energy cosmic ray (UHECR) detectors, is reported. Two independent calibrations of the fluorescence emission induced by a 120 GeV proton beam were employed: Cherenkov light from the beam particle and calibrated light from a nitrogen laser. The fluorescence yield in air at a pressure of 1013 hPa and temperature of 293 K was found to be Y337 ¼ 5:61 � 0:06stat � 0:22syst photons/MeV. When compared to the fluorescence yield currently used by UHECR experiments, this measurement improves the uncertainty by a factor of three, and has a significant impact on the determination of the energy scale of the cosmic ray spectrum.Astroparticle Physics 01/2013; 424:90–102. · 3.22 Impact Factor -
Article: Precise measurement of the absolute fluorescence yield of the 337 nm band in atmospheric gases
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ABSTRACT: A measurement of the absolute fluorescence yield of the 337 nm nitrogen band, relevant to ultra-high energy cosmic ray (UHECR) detectors, is reported. Two independent calibrations of the fluorescence emission induced by a 120 GeV proton beam were employed: Cherenkov light from the beam particle and calibrated light from a nitrogen laser. The fluorescence yield in air at a pressure of 1013 hPa and temperature of 293 K was found to be $Y_{337} = 5.61\pm 0.06_{stat} \pm 0.21_{syst}$ photons/MeV. When compared to the fluorescence yield currently used by UHECR experiments, this measurement improves the uncertainty by a factor of three, and has a significant impact on the determination of the energy scale of the cosmic ray spectrum.10/2012; -
Article: Surgical Endoscopic Vacuum Therapy for Anastomotic Leakage and Perforation of the Upper Gastrointestinal Tract.
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ABSTRACT: INTRODUCTION: Emergency operations for perforations and anastomotic leakage of the upper gastrointestinal tract are associated with a high overall morbidity and mortality rate. An endoscopic vacuum therapy (EVT) has been established successfully for anastomotic leakage after rectal resection but only limited data exist for EVT of the upper GI tract. METHODS: We report on a series of nine patients treated with EVT for defects of the upper intestinal tract between March 2011 and May 2012. In four patients, initial endoscopic sponge placement was performed in combination with open surgical revision. Median follow-up was 189 (range, 51-366) days. RESULTS: In total, 52 vacuum sponges were placed in upper GI defects of nine patients. Indication for EVT were anastomotic leakage after esophageal resection or gastrectomy (n = 5) and iatrogenic or spontaneous esophageal perforations (n = 4). The mean number of sponge insertions was six (range, 1-13) with a mean changing interval of 3.5 days (range, 2-5). A successful vacuum therapy for upper intestinal defects was achieved in eight of nine patients (89 %). CONCLUSION: EVT is a promising approach for postoperative, iatrogenic, or spontaneous lesions of the upper GI tract. If necessary the endoscopic procedure can be combined with operative revision for better control of the local septic focus.Journal of Gastrointestinal Surgery 09/2012; · 2.83 Impact Factor -
Article: A search for ultra-high energy neutrinos in highly inclined events at the Pierre Auger Observatory
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ABSTRACT: The Surface Detector of the Pierre Auger Observatory is sensitive to neutrinos of all flavours above 0.1 EeV. These interact through charged and neutral currents in the atmosphere giving rise to extensive air showers. When interacting deeply in the atmosphere at nearly horizontal incidence, neutrinos can be distinguished from regular hadronic cosmic rays by the broad time structure of their shower signals in the water-Cherenkov detectors. In this paper we present for the first time an analysis based on down-going neutrinos. We describe the search procedure, the possible sources of background, the method to compute the exposure and the associated systematic uncertainties. No candidate neutrinos have been found in data collected from 1 January 2004 to 31 May 2010. Assuming an E^-2 differential energy spectrum the limit on the single flavour neutrino is (E^2 * dN/dE) < 1.74x10^-7 GeV cm^-2 s^-1 sr^-1 at 90% C.L. in the energy range 1x10^17 eV < E < 1x10^20 eV.02/2012; -
Article: Description of Atmospheric Conditions at the Pierre Auger Observatory using the Global Data Assimilation System (GDAS)
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ABSTRACT: Atmospheric conditions at the site of a cosmic ray observatory must be known for reconstructing observed extensive air showers. The Global Data Assimilation System (GDAS) is a global atmospheric model predicated on meteorological measurements and numerical weather predictions. GDAS provides altitude-dependent profiles of the main state variables of the atmosphere like temperature, pressure, and humidity. The original data and their application to the air shower reconstruction of the Pierre Auger Observatory are described. By comparisons with radiosonde and weather station measurements obtained on-site in Malarg\"ue and averaged monthly models, the utility of the GDAS data is shown.01/2012; -
Article: The effect of the geomagnetic field on cosmic ray energy estimates and large scale anisotropy searches on data from the Pierre Auger Observatory
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ABSTRACT: We present a comprehensive study of the influence of the geomagnetic field on the energy estimation of extensive air showers with a zenith angle smaller than $60^\circ$, detected at the Pierre Auger Observatory. The geomagnetic field induces an azimuthal modulation of the estimated energy of cosmic rays up to the ~2% level at large zenith angles. We present a method to account for this modulation of the reconstructed energy. We analyse the effect of the modulation on large scale anisotropy searches in the arrival direction distributions of cosmic rays. At a given energy, the geomagnetic effect is shown to induce a pseudo-dipolar pattern at the percent level in the declination distribution that needs to be accounted for.11/2011; -
Article: Trigger and Aperture of the Surface Detector Array of the Pierre Auger Observatory
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ABSTRACT: The surface detector array of the Pierre Auger Observatory consists of 1600 water-Cherenkov detectors, for the study of extensive air showers (EAS) generated by ultra-high-energy cosmic rays. We describe the trigger hierarchy, from the identification of candidate showers at the level of a single detector, amongst a large background (mainly random single cosmic ray muons), up to the selection of real events and the rejection of random coincidences. Such trigger makes the surface detector array fully efficient for the detection of EAS with energy above $3\times 10^{18}$ eV, for all zenith angles between 0$^\circ$ and 60$^\circ$, independently of the position of the impact point and of the mass of the primary particle. In these range of energies and angles, the exposure of the surface array can be determined purely on the basis of the geometrical acceptance.11/2011; -
Article: The Lateral Trigger Probability function for the Ultra-High Energy Cosmic Ray Showers detected by the Pierre Auger Observatory
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ABSTRACT: In this paper we introduce the concept of Lateral Trigger Probability (LTP) function, i.e., the probability for an extensive air shower (EAS) to trigger an individual detector of a ground based array as a function of distance to the shower axis, taking into account energy, mass and direction of the primary cosmic ray. We apply this concept to the surface array of the Pierre Auger Observatory consisting of a 1.5 km spaced grid of about 1600 water Cherenkov stations. Using Monte Carlo simulations of ultra-high energy showers the LTP functions are derived for energies in the range between 10^{17} and 10^{19} eV and zenith angles up to 65 degs. A parametrization combining a step function with an exponential is found to reproduce them very well in the considered range of energies and zenith angles. The LTP functions can also be obtained from data using events simultaneously observed by the fluorescence and the surface detector of the Pierre Auger Observatory (hybrid events). We validate the Monte-Carlo results showing how LTP functions from data are in good agreement with simulations.11/2011; -
Article: Search for signatures of magnetically-induced alignment in the arrival directions measured by the Pierre Auger Observatory
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ABSTRACT: We present the results of an analysis of data recorded at the Pierre Auger Observatory in which we search for groups of directionally-aligned events (or `multiplets') which exhibit a correlation between arrival direction and the inverse of the energy. These signatures are expected from sets of events coming from the same source after having been deflected by intervening coherent magnetic fields. The observation of several events from the same source would open the possibility to accurately reconstruct the position of the source and also measure the integral of the component of the magnetic field orthogonal to the trajectory of the cosmic rays. We describe the largest multiplets found and compute the probability that they appeared by chance from an isotropic distribution. We find no statistically significant evidence for the presence of multiplets arising from magnetic deflections in the present data.11/2011; -
Article: The Pierre Auger Observatory II: Studies of Cosmic Ray Composition and Hadronic Interaction models
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ABSTRACT: Studies of the composition of the highest energy cosmic rays with the Pierre Auger Observatory, including examination of hadronic physics effects on the structure of extensive air showers.07/2011; -
Article: The Pierre Auger Observatory III: Other Astrophysical Observations
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ABSTRACT: Astrophysical observations of ultra-high-energy cosmic rays with the Pierre Auger Observatory07/2011; -
Article: The Pierre Auger Observatory IV: Operation and Monitoring
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ABSTRACT: Technical reports on operations and monitoring of the Pierre Auger Observatory07/2011; -
Article: The Pierre Auger Observatory V: Enhancements
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ABSTRACT: Ongoing and planned enhancements of the Pierre Auger Observatory07/2011; -
Article: The Pierre Auger Observatory I: The Cosmic Ray Energy Spectrum and Related Measurements
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ABSTRACT: Studies of the cosmic ray energy spectrum at the highest energies with the Pierre Auger Observatory07/2011; -
Article: The Pierre Auger Observatory IV: Operation and Monitoring
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ABSTRACT: Technical reports on operations and monitoring of the Pierre Auger Observatory06/2011; -
Article: Anisotropy and chemical composition of ultra-high energy cosmic rays using arrival directions measured by the Pierre Auger Observatory
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ABSTRACT: 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 due to nuclei with charge $Z$, and under reasonable assumptions about the acceleration process, these observations imply stringent constraints on the allowed proton fraction at the lower energies.06/2011; -
Article: Search for First Harmonic Modulation in the Right Ascension Distribution of Cosmic Rays Detected at the Pierre Auger Observatory
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ABSTRACT: We present the results of searches for dipolar-type anisotropies in different energy ranges above $2.5\times 10^{17}$ eV with the surface detector array of the Pierre Auger Observatory, reporting on both the phase and the amplitude measurements of the first harmonic modulation in the right-ascension distribution. Upper limits on the amplitudes are obtained, which provide the most stringent bounds at present, being below 2% at 99% $C.L.$ for EeV energies. We also compare our results to those of previous experiments as well as with some theoretical expectations.03/2011; -
Article: Precise Measurement of the Absolute Yield of Fluorescence Photons in Atmospheric Gases
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ABSTRACT: We have performed a measurement of the absolute yield of fluorescence photons at the Fermilab Test Beam. A systematic uncertainty at 5% level was achieved by the use of Cherenkov radiation as a reference calibration light source. A cross-check was performed by an independent calibration using a laser light source. A significant improvement on the energy scale uncertainty of Ultra-High Energy Cosmic Rays is expected.01/2011; -
Article: Update on the correlation of the highest energy cosmic rays with nearby extragalactic matter
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ABSTRACT: Data collected by the Pierre Auger Observatory through 31 August 2007 showed evidence for anisotropy in the arrival directions of cosmic rays above the Greisen-Zatsepin-Kuz'min energy threshold, \nobreak{$6\times 10^{19}$eV}. The anisotropy was measured by the fraction of arrival directions that are less than $3.1^\circ$ from the position of an active galactic nucleus within 75 Mpc (using the V\'eron-Cetty and V\'eron $12^{\rm th}$ catalog). An updated measurement of this fraction is reported here using the arrival directions of cosmic rays recorded above the same energy threshold through 31 December 2009. The number of arrival directions has increased from 27 to 69, allowing a more precise measurement. The correlating fraction is $(38^{+7}_{-6})%$, compared with $21%$ expected for isotropic cosmic rays. This is down from the early estimate of $(69^{+11}_{-13})%$. The enlarged set of arrival directions is examined also in relation to other populations of nearby extragalactic objects: galaxies in the 2 Microns All Sky Survey and active galactic nuclei detected in hard X-rays by the Swift Burst Alert Telescope. A celestial region around the position of the radiogalaxy Cen A has the largest excess of arrival directions relative to isotropic expectations. The 2-point autocorrelation function is shown for the enlarged set of arrival directions and compared to the isotropic expectation. Comment: Accepted for publication in Astroparticle Physics on 31 August 201009/2010;
Top co-authors
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Institutions
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2012
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University of Rostock
Rostock, Mecklenburg-Vorpommern, Germany
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2010
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Universidad Tecnológica Nacional
San Nicolás de los Arroyos, Provincia de Buenos Aires, Argentina
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2008–2010
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Ohio State University
- Department of Physics
Columbus, OH, USA
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