We review some of the recent progress in our knowledge about high-energy cosmic rays, with an emphasis on the interpretation of the different observational results. We discuss the effects that are ...relevant to shape the cosmic ray spectrum and the explanations proposed to account for its features and for the observed changes in composition. The physics of air-showers is summarized and we also present the results obtained on the proton–air cross section and on the muon content of the showers. We discuss the cosmic ray propagation through magnetic fields, the effects of diffusion and of magnetic lensing, the cosmic ray interactions with background radiation fields and the production of secondary neutrinos and photons. We also consider the cosmic ray anisotropies, both at large and small angular scales, presenting the results obtained from the TeV up to the highest energies and discuss the models proposed to explain their origin.
► Analysis of data recorded at the Pierre Auger Observatory. ► We search for groups of aligned events which exhibit a correlation between arrival direction and the inverse of the energy. ► We ...describe the largest multiplets found. ► There is no statistically significant evidence for the presence of multiplets arising from magnetic deflections.
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.
Results from the Pierre Auger Observatory Zavrtanik, Danilo
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2011, Volume:
630, Issue:
1
Journal Article
Peer reviewed
The southern part of the Pierre Auger Observatory located in Province of Mendoza, Argentina, is now completed and fully operational. Data are routinely recorded since 2004, even during the ...construction phase. It consists of a ground array of more than 1.600 water-Cherenkov detectors spread over an area of 3000
km
2, overlooked by 24 wide-angle fluorescence telescopes placed in four sites on the array boundary. Southern Observatory is taking data in hybrid mode making it the first hybrid detector for studying the origin and the nature of cosmic rays at extreme energies. Current characteristics of the observatory and recent results on primary cosmic ray spectrum, arrival directions and composition are presented.
The status of the Pierre Auger Observatory is described. Recent measurements from the Observatory relating to the arrival direction distribution, mass composition and energy spectrum above 1018eV are ...presented. No anisotropy has yet been detected. From measurements of the variation of the depth of shower maximum with energy, there are indications—if models of high-energy interactions are correct—that the mass composition is not proton dominated at the highest energies. A flattening of the slope of the energy spectrum from −3.30±0.06 to −2.62±0.02 is observed at 4.5×1018eV while above 3.6×1019eV the spectrum steepens with the slope becoming −4.1±0.4. Because of the composition result, caution needs to be observed over interpretation of the steepening as the long-sought Greisen–Zatsepin–Kuzmin effect. The results are discussed in the context of similar data from the AGASA and HiRes projects and are compared with some models for the propagation of high-energy cosmic rays.
Ultra High Energy Cosmic Rays (UHECRs) represent the most energetic source of elementary particles available to scientists. They have macroscopic energies, exceeding 5 × 10
19
eV, and as yet ...unidentified sources. Unfortunately, their flux is as low as one particle per century per square kilometre, requiring dedicated detectors with huge apertures to obtain high-quality and statistically significant data-sets. Over the last three to four decades, a few tens of events at extreme energies were detected by ground-based cosmic ray detectors, opening a new window in the field of astroparticle physics. In this article, the physics of cosmic rays is reviewed briefly. We present a short history and the present status of the field mainly from an experimental point of view. Special attention is given to the Pierre Auger Observatory, the world's largest operating hybrid detector. The most recent and fascinating results are also presented and discussed. Finally, some attention is given to the next generation of detectors devoted to the exploration of the highest energy ranges, which is likely to dramatically increase our knowledge about UHECRs in the near future.
The Large Area Telescope on board the \textit{Fermi} satellite (\textit{Fermi}-LAT) detected more than 1.6 million cosmic-ray electrons/positrons with energies above 60 GeV during its first year of ...operation. The arrival directions of these events were searched for anisotropies of angular scale extending from $\sim$ 10 $^\circ$ up to 90$^\circ$, and of minimum energy extending from 60 GeV up to 480 GeV. Two independent techniques were used to search for anisotropies, both resulting in null results. Upper limits on the degree of the anisotropy were set that depended on the analyzed energy range and on the anisotropy's angular scale. The upper limits for a dipole anisotropy ranged from $\sim0.5%$ to $\sim10%$.
Stacks of cellulose nitrate and cellulose triacetate plastic nuclear track detectors were exposed on a russian satellite in a low earth orbit during the solar particle events in October 1989. ...Extremely high fluences of solar particles with nuclear charges equal to or greater than 6 were registered. In CTA a charge identification for Z= 8–14 with a resolution of 0.5 charge units was achieved. Energy spectra and arrival directions of the detected particles were measured in both detector materials. The distribution of the arrival directions for ions in CTA shows a significant contribution of particles impinging from below the horizon.
Trapped heavy ions on LDEF Beaujean, R.; Barz, S.; Jonathal, D. ...
Radiation measurements,
1995, 1995-1-00, Volume:
25, Issue:
1
Journal Article
Peer reviewed
Plastic nuclear track detectors were used to study below-cutoff heavy ions in a 28.5 degree inclination orbit aboard the NASA satellite Long Duration Exposure Facility (LDEF). Particle arrival ...directions and energy spectra were measured in stacks of CR-39 and cellulose nitrate. The obtained results for particles with energies below 50 MeV/nuc are interpreted as evidence for the detection of a trapped component registered in the South Atlantic region at values of L = 1.4−1.7.
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