Related papers: Probing UHECR sources - Constraints from cosmic-ra…
The origin and nature of ultrahigh-energy cosmic rays (UHECRs) are one of the most intriguing mysteries in particle astrophysics and astronomy. The two largest observatories, the Pierre Auger Observatory and the Telescope Array Experiment,…
The origin of ultra-high energy cosmic rays (UHECRs) and neutrinos is still a mystery. Hadronic acceleration theory suggests that they should originate in the same sources (astrophysical or cosmological), together with gamma-rays. While…
Ultra High Energy Cosmic Rays (UHECRs) hit the Earth's atmosphere with energies exceeding $10^{18}$ eV. This is the same energy as carried by a tennis ball moving at 100 km/h, but concentrated on a sub-atomic particle. UHECRs are so rare…
We consider the recent results on UHECR (Ultra High Energy Cosmic Ray), clustering, composition, distribution in the sky, from the energy of several EeV with the dipole anisotropy up to the highest ones. We have suggested since 2008 and we…
The origin of Ultra--High Energy ($E \gsim 10^{20}$ eV) Cosmic Rays (UHECR) remains mysterious. I discuss ``top--down'' models, where UHECR originate from the decay of very massive, long--lived particles. I summarize the calculation of the…
Since astrophysical neutrinos are produced in the interactions of cosmic rays, identifying the origin of cosmic rays using directional correlations with neutrinos is one of the most interesting possibilities of the field. For that purpose,…
Recent advances in measuring and interpreting cosmic rays from the spectral ankle to the highest energies are briefly reviewed. The prime question at the highest energies is about the origin of the flux suppression observed at E ~ 4x10^{19}…
The origin of cosmic rays is one of the major unresolved questions in astrophysics. In particular, the highest energy cosmic rays observed possess macroscopic energies and their origin is likely associated with the most energetic processes…
We present a combined fit of a simple astrophysical model of UHECR sources to both the energy spectrum and mass composition data measured by the Pierre Auger Observatory. The fit has been performed for energies above 5 EeV, i.e. the region…
Ultra-high energy cosmic rays (UHECRs) may originate from the decay of massive relic particles in the dark halo of the Galaxy, or they may be produced by supermassive black holes in the nuclei of nearby galaxies. The anisotropy in the…
The energy spectrum and mass composition of ultra-high energy cosmic rays inferred at the Pierre Auger Observatory are used to derive a benchmark scenario for the emission mechanisms at play in extragalactic accelerators as well as for…
The origin of the highest-energy cosmic rays remains a mystery. The lack of a high energy cutoff in the cosmic ray spectrum together with an apparently isotropic distribution of arrival directions have strongly constrained most models…
A fundamental question that can be answered in the next decade is: WHAT IS THE ORIGIN OF THE HIGHEST ENERGY COSMIC PARTICLES? The discovery of the sources of the highest energy cosmic rays will reveal the workings of the most energetic…
Since their first observation in 1962, the existence of Ultra High Energy Cosmic Rays (UHECR) remains a mystery in modern astrophysics. Those cosmic rays, with energies well above 50 EeV ($50\times 10^{18}$eV), can hardly be accelerated,…
Ultrahigh energy cosmic rays are the most energetic of any subatomic particles ever observed in nature. The quest for their mysterious origin is currently a major scientific challenge. Here we explore the possibility that these particles…
The discoveries of the GZK cutoff with the HiRes and Auger Observatories and the discovery by Auger of clustering of >~60 EeV ultra-high energy cosmic rays (UHECRs) towards nearby <~75 Mpc) AGNs along the supergalactic plane establishes the…
Ultra-high energy cosmic rays (UHECRs) are the most energetic particles observed and serve as a probe of the extreme universe. A key question to understanding the violent processes responsible for their acceleration is identifying which…
We have published the energy spectrum of ultra-high energy cosmic rays (UHECRs) for E > 10^18.2 eV from our first 5-year observation with the surface detectors of Telescope Array. We found two breaking points in the power-law spectrum, a…
The present situation with regard to experimental data on ultra high-energy cosmic rays is briefly reviewed. Whilst detailed knowledge of the shape of the energy spectrum is still lacking, it is clear that events above 10^20 eV do exist.…
Observations of cosmic rays have been improving at all energies, with higher statistics and reduced systematics. Fundamental questions remain regarding the origins of cosmic rays both within the Galaxy and in extragalactic sources, and new…