48 research outputs found
Measurement of the proton-air cross section at root s=57 TeV with the Pierre Auger Observatory
No full textWe report a measurement of the proton-air cross section for particle production at the center-of-mass energy per nucleon of 57 TeV. This is derived from the distribution of the depths of shower maxima observed with the Pierre Auger Observatory: systematic uncertainties are studied in detail. Analyzing the tail of the distribution of the shower maxima, a proton-air cross section of [505±22(stat)₋₃₆⁺²⁸(syst)] mb is found.K. B Barber.... J.A. Bellido.... R.W. Clay.... M.J. Cooper.... B.R. Dawson.... T.A. Harrison.... A.E. Herve.... V.C. Holmes.... J. Sorokin.... P. Wahrlich.... B.J. Whelan.... M. G. Winnick... et al.(The Pierre Auger Collaboration
Description of atmospheric conditions at the Pierre Auger Observatory using the Global Data Assimilation System (GDAS)
No full textAtmospheric 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 Malargüe and averaged monthly models, the utility of the GDAS data is shown. © 2012 Elsevier B.V. All rights reserved.The Pierre Auger Collaboration... K. B. Barber... J. A. Bellido... R. W. Clay... M. J. Cooper... B. R. Dawson... T. A. Harrison... A. E. Herve... V. C. Holmes... J. Sorokin... P. Wahrlich... B. J. Whelan... et al
Interpretation of the depths of maximum of extensive air showers measured by the Pierre Auger Observatory
No full textCollaboration members: K.B. Barber, J.A. Bellido, R.W. Clay, M.J. Cooper, B.R. Dawson, T.D. Grubb, T.A. Harrison, A.E. Herve, G.C. Hill, V.C. Holmes, M. Malacari, S.J. Saffi, and P. Wahrlich of the University of Adelaide, Adelaide, South Australia, AustraliaTo interpret the mean depth of cosmic ray air shower maximum and its dispersion, we parametrize those two observables as functions of the first two moments of the ln A distribution. We examine the goodness of this simple method through simulations of test mass distributions. The application of the parameterization to Pierre Auger Observatory data allows one to study the energy dependence of the mean ln A and of its variance under the assumption of selected hadronic interaction models. We discuss possible implications of these dependences in term of interaction models and astrophysical cosmic ray sources.The Pierre Auger collaboratio
The Lateral Trigger Probability function for the Ultra-High Energy Cosmic Ray showers detected by the Pierre Auger Observatory
No full textIn 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 1017 and 1019 eV and zenith angles up to 65°. 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. © 2011 Published by Elsevier B.V.The Pierre Auger Collaboration... P. Abreu... K. B. Barber... J. A. Bellido... R. W. Clay... M. J. Cooper... B. R. Dawson... A. E. Herve... V. C. Holmes... J. S. Sorokin... P. S. Wahrlich... M. G. Winnick... et al.http://www.journals.elsevier.com/astroparticle-physics
Bounds on the density of sources of ultra-high energy cosmic rays from the Pierre Auger Observatory
No full textContribution Members: K.B. Barber, J.A. Bellido, R.W. Clay, M.J. Cooper, B.R. Dawson, T.A. Harrison, A.E. Herve, G.C. Hill, V.C. Holmes, M. Malacari, S.J. Saffi, J. Sorokin, P. Wahrlich for the University of Adelaide, Adelaide, S.A., AustraliaWe derive lower bounds on the density of sources of ultra-high energy cosmic rays from the lack of significant clustering in the arrival directions of the highest energy events detected at the Pierre Auger Observatory. The density of uniformly distributed sources of equal intrinsic intensity was found to be larger than ~ (0.06−5) × 10⁻⁴ Mpc⁻³ at 95% CL, depending on the magnitude of the magnetic deflections. Similar bounds, in the range (0.2−7) × 10⁻⁴ Mpc⁻³, were obtained for sources following the local matter distribution.The Pierre Auger collaboratio
Searches for large-scale anisotropy in the arrival directions of cosmic rays detected above energy of 10 eV at the Pierre Auger Observatory and the telescope array
No full textContains fulltext :
132623pub.pdf (Publisher’s version ) (Open Access)
Contains fulltext :
132623.pdf (Author’s version preprint ) (Open Access
Large-scale distribution of arrival directions of cosmic rays detected above 10(18) ev at the Pierre Auger observatory
No full textA thorough search for large-scale anisotropies in the distribution of arrival directions of cosmic rays detected above 10¹⁸ eV at the Pierre Auger Observatory is presented. This search is performed as a function of both declination and right ascension in several energy ranges above 10¹⁸ eV, and reported in terms of dipolar and quadrupolar coefficients. Within the systematic uncertainties, no significant deviation from isotropy is revealed. Assuming that any cosmic-ray anisotropy is dominated by dipole and quadrupole moments in this energy range, upper limits on their amplitudes are derived. These upper limits allow us to test the origin of cosmic rays above 10¹⁸ eV from stationary Galactic sources densely distributed in the Galactic disk and predominantly emitting light particles in all directions.The Pierre Auger Collaboration, P. Abreu ... K. B. Barber ... J. A. Bellido ... R. W. Clay ... M. J. Cooper ... B. R. Dawson ... T. A. Harrison ... A. E. Herve, G. C. Hill ... V. C. Holmes ... J. Sorokin ... P. Wahrlich ... B. J. Whelan ... et al
Update on the correlation of the highest energy cosmic rays with nearby extragalactic matter
No full textData 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, 6 × 1019 eV. The anisotropy was measured by the fraction of arrival directions that are less than 3.1° from the position of an active galactic nucleus within 75 Mpc (using the Véron-Cetty and Véron 12th 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 38-6+7%, compared with 21% expected for isotropic cosmic rays. This is down from the early estimate of 69-13+11%. 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. © 2010 Elsevier B.V. All rights reserved.The Pierre Auger Collaboration. P.Abreu...K.Barber...C.Bellido...R.Clay...M.Cooper...B.Dawson...A.Herve...V.Holmes...J.Sorokin...P. Wahrlich...B.Whelan...M.Winnick...and M. Ziolkowskial, et.al.http://www.elsevier.com/wps/find/journaldescription.cws_home/523319/description#descriptio
Ultrahigh energy neutrinos at the Pierre Auger observatory
No full textThe observation of ultrahigh energy neutrinos (UHEνs) has become a priority in experimental astroparticle physics. UHEνs can be detected with a variety of techniques. In particular, neutrinos can interact in the atmosphere (downward-going ν) or in the Earth crust (Earth-skimming ν), producing air showers that can be observed with arrays of detectors at the ground. With the surface detector array of the Pierre Auger Observatory we can detect these types of cascades. The distinguishing signature for neutrino events is the presence of very inclined showers produced close to the ground (i.e., after having traversed a large amount of atmosphere). In this work we review the procedure and criteria established to search for UHEνs in the data collected with the ground array of the Pierre Auger Observatory. This includes Earth-skimming as well as downward-going neutrinos. No neutrino candidates have been found, which allows us to place competitive limits to the diffuse flux of UHEνs in the EeV range and above.P. Abreu ... K. B. Barber ... J. A. Bellido ... R. W. Clay ... M. J. Cooper ... B. R. Dawson ... T. A. Harrison ... A. E. Herve ... V. C. Holmes ... J. Sorokin ... P. Wahrlich ... B. J. Whelan ... et al
Olefin Epoxidation in Aqueous Phase Using Ionic-Liquid Catalysts
No full textHydrophobic imidazolium-based ionic liquids (IL) act as catalysts for the epoxidation of unfunctionalized olefins in water using hydrogen peroxide as oxidant. Although the catalysts are insoluble in both the substrate and in water, surprisingly, they are very well soluble in aqueous H2O2 solution, owing to perrhenate-H2O2 interactions. Even more remarkably, the presence of the catalyst also boosts the solubility of substrate in water. This effect is crucially dependent on the cation design. Hence, the imidazolium perrhenates enable both the transfer of hydrophobic substrate into the aqueous phase, and serve as actual catalysts, which is unprecedented. At the end of the reaction and in absence of H2O2 the IL catalyst forms a third phase next to the lipophilic product and water and can easily be recycled.</p
