13 research outputs found
Astrophysical Origins of Ultrahigh Energy Cosmic Rays
In the first part of this review we discuss the basic observational features
at the end of the cosmic ray energy spectrum. We also present there the main
characteristics of each of the experiments involved in the detection of these
particles. We then briefly discuss the status of the chemical composition and
the distribution of arrival directions of cosmic rays. After that, we examine
the energy losses during propagation, introducing the Greisen-Zaptsepin-Kuzmin
(GZK) cutoff, and discuss the level of confidence with which each experiment
have detected particles beyond the GZK energy limit. In the second part of the
review, we discuss astrophysical environments able to accelerate particles up
to such high energies, including active galactic nuclei, large scale galactic
wind termination shocks, relativistic jets and hot-spots of Fanaroff-Riley
radiogalaxies, pulsars, magnetars, quasar remnants, starbursts, colliding
galaxies, and gamma ray burst fireballs. In the third part of the review we
provide a brief summary of scenarios which try to explain the super-GZK events
with the help of new physics beyond the standard model. In the last section, we
give an overview on neutrino telescopes and existing limits on the energy
spectrum and discuss some of the prospects for a new (multi-particle)
astronomy. Finally, we outline how extraterrestrial neutrino fluxes can be used
to probe new physics beyond the electroweak scale.Comment: Higher resolution version of Fig. 7 is available at
http://www.angelfire.com/id/dtorres/down3.html. Solicited review article
prepared for Reports on Progress in Physics, final versio
An upper limit to the photon fraction in cosmic rays above 10^19 eV from the Pierre Auger Observatory
An upper limit of 16% (at 95% c.l.) is derived for the photon fraction in cosmic rays with energies above 10^19 eV, based on observations of the depth of shower maximum performed with the hybrid detector of the Pierre Auger Observatory. This is the first such limit on photons obtained by observing the fluorescence light profile of air showers. This upper limit confirms and improves on previous results from the Haverah Park and AGASA surface arrays. Additional data recorded with the Auger surface detectors for a subset of the event sample, support the conclusion that a photon origin of the observed events is not favoured
An upper limit to the photon fraction in cosmic rays above 10^19 eV from the Pierre Auger Observatory
31 pages, 11 figures, 2 tables. Minor changes, appendix expanded, conclusions unchanged; accepted by Astroparticle PhysicsAn upper limit of 16% (at 95% c.l.) is derived for the photon fraction in cosmic rays with energies greater than 10^19 eV, based on observations of the depth of shower maximum performed with the hybrid detector of the Pierre Auger Observatory. This is the first such limit on photons obtained by observing the fluorescence light profile of air showers. This upper limit confirms and improves on previous results from the Haverah Park and AGASA surface arrays. Additional data recorded with the Auger surface detectors for a subset of the event sample, support the conclusion that a photon origin of the observed events is not favored
Correlation of the highest-energy cosmic rays with nearby extragalactic objects
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 × 1019 electron volts and the positions of active galactic nuclei (AGN) lying within ∼75 megaparsecs. We rejected the hypothesis of an isotropic distribution of these cosmic rays with at least a 99% confidence level from a prescribed a priori test. The correlation we observed is compatible with the hypothesis that the highest-energy particles originate from nearby extragalactic sources whose flux has not been substantially reduced by interaction with the cosmic background radiation. AGN or objects having a similar spatial distribution are possible sources
Upper Limit on the Diffuse Flux of UHE tau neutrinos from the Pierre Auger Observatory.
The surface detector array of the Pierre Auger Observatory is sensitive to
Earth-skimming tau-neutrinos that interact in the Earth's crust. Tau
leptons from 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 31
August 2007 is used to place an upper limit on the diffuse flux of
at EeV energies. Assuming an differential energy spectrum the
limit set at 90 % C.L. is GeV cm s sr in the energy range
eV.Comment: 14 pages, 3 figure
Properties and performance of the prototype instrument for the Pierre Auger Observatory
Copyright © 2003 Elsevier B.V. All rights reserved.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 1018 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 will be used in the full instrument to be tested under field conditions. In this paper, the properties and performance of these sub-systems are described and their success illustrated with descriptions of some of the events recorded thus far.Auger Collaboration, ..., J. A. Bellido, ..., R. W. Clay, ..., B. R. Dawson, ..., G. J. Thornton, ..., N. R. Wild, et al.http://www.elsevier.com/wps/find/journaldescription.cws_home/505701/description#descriptio
Correlation of the Highest-energy Cosmic Rays with the Positions of Nearby Active Galactic Nuclei.
Data collected by the Pierre Auger Observatory provide evidence for
anisotropy in the arrival directions of the cosmic rays with the highest
energies, which are correlated with the positions of relatively nearby active
galactic nuclei (AGN) \cite{science}. The correlation has maximum significance
for cosmic rays with energy greater than ~ 6x10^{19}$ eV and AGN at a distance
less than ~ 75 Mpc. We have confirmed the anisotropy at a confidence level of
more than 99% through a test with parameters specified {\em a priori}, using an
independent data set. The observed correlation is compatible with the
hypothesis that cosmic rays with the highest energies originate from
extra-galactic sources close enough so that their flux is not significantly
attenuated by interaction with the cosmic background radiation (the
Greisen-Zatsepin-Kuz'min effect). The angular scale of the correlation observed
is a few degrees, which suggests a predominantly light composition unless the
magnetic fields are very weak outside the thin disk of our galaxy. Our present
data do not identify AGN as the sources of cosmic rays unambiguously, and other
candidate sources which are distributed as nearby AGN are not ruled out. We
discuss the prospect of unequivocal identification of individual sources of the
highest-energy cosmic rays within a few years of continued operation of the
Pierre Auger Observatory.Comment: 33 pages, 8 figures, submitted to Astropart. phys. Now match the
published versio