102 research outputs found
Progress in Monte Carlo design and optimization of the Cherenkov Telescope Array
The Cherenkov Telescope Array (CTA) will be an instrument covering a wide
energy range in very-high-energy (VHE) gamma rays. CTA will include several
types of telescopes, in order to optimize the performance over the whole energy
range. Both large-scale Monte Carlo (MC) simulations of CTA super-sets
(including many different possible CTA layouts as sub-sets) and smaller-scale
simulations dedicated to individual aspects were carried out and are on-going.
We summarize results of the prior round of large-scale simulations, show where
the design has now evolved beyond the conservative assumptions of the prior
round and present first results from the on-going new round of MC simulations.Comment: 4 pages, 5 figures. In Proceedings of the 33rd International Cosmic
Ray Conference (ICRC2013), Rio de Janeiro (Brazil). All CTA contributions at
arXiv:1307.223
Implications of the cosmic ray spectrum for the mass composition at the highest energies
The significant attenuation of the cosmic-ray flux above eV
suggests that the observed high-energy spectrum is shaped by the so-called GZK
effect. This interaction of ultra-high-energy cosmic rays (UHECRs) with the
ambient radiation fields also affects their composition. We review the effect
of photo-dissociation interactions on different nuclear species and analyze the
phenomenology of secondary proton production as a function of energy. We show
that, by itself, the UHECR spectrum does not constrain the cosmic-ray
composition at their extragalactic sources. While the propagated composition
(i.e., as observed at Earth) cannot contain significant amounts of intermediate
mass nuclei (say between He and Si), whatever the source composition, and while
it is vastly proton-dominated when protons are able to reach energies above
eV at the source, we show that the propagated composition can be
dominated by Fe and sub-Fe nuclei at the highest energies, either if the
sources are very strongly enriched in Fe nuclei (a rather improbable
situation), or if the accelerated protons have a maximum energy of a few
eV at the sources. We also show that in the latter cases, the
expected flux above eV is very much reduced compared to the case
when protons dominate in this energy range, both at the sources and at Earth.Comment: 16 pages, 7 figure
Progress in Monte Carlo design and optimization of the Cherenkov Telescope Array
The Cherenkov Telescope Array (CTA) will be an instrument covering a wide energy range in very-high-energy (VHE) gamma rays. CTA will include several types of telescopes, in order to optimize the performance over the whole energy range. Both large-scale Monte Carlo (MC) simulations of CTA super-sets (including many different possible CTA layouts as sub-sets) and smaller-scale simulations dedicated to individual aspects were carried out and are on-going. We summarize results of the prior round of large-scale simulations, show where the design has now evolved beyond the conservative assumptions of the prior round and present first results from the on-going new round of MC simulations.Fil: Bernlöhr, K.. Max-Planck-Institut fur Kernphysik; AlemaniaFil: Barnacka, A.. Polish Academy of Sciences; ArgentinaFil: Becherini, Y.. Ăcole Polytechnique; FranciaFil: Blanch Bigas, O.. IFAE; EspañaFil: Bouvier, A.. University of California; Estados UnidosFil: Carmona, E.. Max-Planck-Institut fur Physik; AlemaniaFil: Colin, P.. Max-Planck-Institut fur Physik; AlemaniaFil: Decerprit, G.. DESY; AlemaniaFil: di Pierro, F.. Osservatorio Astrofisico di Torino dellâIstituto Nazionale di Astrofisica; ItaliaFil: Dubois, F.. Universidad Complutense de Madrid; EspañaFil: Farnier, C.. Stockholm University; SueciaFil: Funk, S.. Kavli Institute for Particle Astrophysics and Cosmology; Estados UnidosFil: Hermann, G.. Max-Planck-Institut fur Kernphysik; AlemaniaFil: Hinton, J. A.. The University of Leicester; Reino UnidoFil: Humensky, T. B.. Columbia University; Estados UnidosFil: Jogler, T.. Kavli Institute for Particle Astrophysics and Cosmology; Estados UnidosFil: KhĂ©lifi, B.. Ăcole Polytechnique; FranciaFil: Kihm, T.. Max-Planck-Institut fur Kernphysik; AlemaniaFil: Komin, N.. Universite de Savoie; FranciaFil: Lenain, J. -P.. UniversitĂ© Denis Diderot Paris 7; FranciaFil: LĂłpez Coto, R.. IFAE; EspañaFil: Maier, G.. DESY; AlemaniaFil: Mazin, D.. Max-Planck-Institut fur Physik; AlemaniaFil: Medina, Maria Clementina. Provincia de Buenos Aires. GobernaciĂłn. ComisiĂłn de Investigaciones CientĂficas. Instituto Argentino de RadioastronomĂa. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico Conicet - La Plata. Instituto Argentino de RadioastronomĂa; ArgentinaFil: Moralejo, A.. IFAE; EspañaFil: Moderski, R.. Polish Academy of Sciences; ArgentinaFil: Nolan, S. J.. Durham University; Reino UnidoFil: Ohm, S.. The University of Leicester; Reino UnidoFil: de Oña Wilhelmi, E.. Max-Planck-Institut fur Kernphysik; Alemania33rd International Cosmic Ray ConferenceRĂo de JaneiroBrasilBrazilian Physical Societ
Anisotropy and chemical composition of ultra-high energy cosmic rays using arrival directions measured by the Pierre Auger Observatory
The Pierre Auger Collaboration has reported evidence for anisotropy in the
distribution of arrival directions of the cosmic rays with energies
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
are heavy nuclei with charge , the proton component of the
sources should lead to excesses in the same regions at energies . We here
report the lack of anisotropies in these directions at energies above
(for illustrative values of ). If the anisotropies
above are due to nuclei with charge , and under reasonable
assumptions about the acceleration process, these observations imply stringent
constraints on the allowed proton fraction at the lower energies
Operations of and Future Plans for the Pierre Auger Observatory
Technical reports on operations and features of the Pierre Auger Observatory,
including ongoing and planned enhancements and the status of the future
northern hemisphere portion of the Observatory. Contributions to the 31st
International Cosmic Ray Conference, Lodz, Poland, July 2009.Comment: Contributions to the 31st ICRC, Lodz, Poland, July 200
Measurement of the Depth of Maximum of Extensive Air Showers above 10^18 eV
We describe the measurement of the depth of maximum, Xmax, of the
longitudinal development of air showers induced by cosmic rays. Almost four
thousand 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 found to
evolve with energy at a rate of (106 +35/-21) g/cm^2/decade below 10^(18.24 +/-
0.05) eV and (24 +/- 3) g/cm^2/decade above this energy. The measured
shower-to-shower fluctuations decrease from about 55 to 26 g/cm^2. The
interpretation of these results in terms of the cosmic ray mass composition is
briefly discussed.Comment: Accepted for publication by PR
The Pierre Auger Observatory III: Other Astrophysical Observations
Astrophysical observations of ultra-high-energy cosmic rays with the Pierre
Auger ObservatoryComment: Contributions to the 32nd International Cosmic Ray Conference,
Beijing, China, August 201
Update on the correlation of the highest energy cosmic rays with nearby extragalactic matter
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{eV}. The
anisotropy was measured by the fraction of arrival directions that are less
than from the position of an active galactic nucleus within 75 Mpc
(using the V\'eron-Cetty and V\'eron 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 , compared
with expected for isotropic cosmic rays. This is down from the early
estimate of . 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 201
Advanced functionality for radio analysis in the Offline software framework of the Pierre Auger Observatory
The advent of the Auger Engineering Radio Array (AERA) necessitates the
development of a powerful framework for the analysis of radio measurements of
cosmic ray air showers. As AERA performs "radio-hybrid" measurements of air
shower radio emission in coincidence with the surface particle detectors and
fluorescence telescopes of the Pierre Auger Observatory, the radio analysis
functionality had to be incorporated in the existing hybrid analysis solutions
for fluoresence and surface detector data. This goal has been achieved in a
natural way by extending the existing Auger Offline software framework with
radio functionality. In this article, we lay out the design, highlights and
features of the radio extension implemented in the Auger Offline framework. Its
functionality has achieved a high degree of sophistication and offers advanced
features such as vectorial reconstruction of the electric field, advanced
signal processing algorithms, a transparent and efficient handling of FFTs, a
very detailed simulation of detector effects, and the read-in of multiple data
formats including data from various radio simulation codes. The source code of
this radio functionality can be made available to interested parties on
request.Comment: accepted for publication in NIM A, 13 pages, minor corrections to
author list and references in v
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