Related papers: Testing Brane World Models with Ultra High Energy …
We have calculated the probability that the clustering of arrival directions of ultra-high energy cosmic rays (UHECRs) is consistent with a finite number of uniformly distributed proton sources. The case of a continuous source distribution…
From direct observations of the longitudinal development of ultra-high energy air showers performed with the Pierre Auger Observatory, upper limits of 3.8%, 2.4%, 3.5% and 11.7% (at 95% c.l.) are obtained on the fraction of cosmic-ray…
We propose a novel model to produce ultrahigh-energy cosmic-rays (UHECRs) in gamma-ray burst jets. After the prompt gamma-ray emission, hydrodynamical turbulence is excited in the GRB jets at or before the afterglow phase. The mildly…
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 unified models of astrophysical sources to account for ultrahigh-energy cosmic rays (UHECRs) and high-energy cosmic neutrinos with energies greater than 100 TeV have been discussed. Based on model-independent arguments, we argue that if…
Cosmic ray particles with energies in excess of 10**(20) eV have been detected. The sources as well as the physical mechanism(s) responsible for endowing cosmic ray particles with such enormous energies are unknown. This report gives a…
Cosmic rays from outer space enter the atmosphere with energies of up to 10^{11} GeV. The initial particle or a secondary hadron inside the shower may then interact with an air nucleon to produce nonstandard particles. In this article we…
Extensive air showers are complex objects, resulting of billions of particle reactions initiated by single cosmic ray at ultra-high-energy. Their characteristics are sensitive both to the mass of the primary cosmic ray and to the details of…
The composition of ultra-high energy cosmic rays is still poorly known and constitutes a very important topic in the field of high-energy astrophysics. Detection of ultra-high energy cosmic rays is carried out via the extensive air showers…
The first interactions of photon-induced showers are of electromagnetic nature, and the transfer of energy to the hadron/muon channel is reduced with respect to the bulk of hadron-induced showers. This results in a lower number of secondary…
We discuss the basic features of the propagation of Ultra High Energy Cosmic Rays in astrophysical backgrounds, comparing two alternative computation schemes to compute the expected fluxes. We also discuss the issue of the transition among…
We present an analysis of the correlation between the depth of the maximum of air-shower profiles and the signal in water-Cherenkov stations in events registered simultaneously by the fluorescence and surface detectors of the Pierre Auger…
We study the production of cosmogenic neutrinos and photons during the extragalactic propagation of ultra-high-energy cosmic rays (UHECRs). For a wide range of models in cosmological evolution of source luminosity, composition and maximum…
In the last years a general consensus has emerged on the use of ultra-high energy cosmic rays (UHECR) data as a powerful probe of the validity of special relativity. This applies in particular to the propagation of cosmic rays from their…
The nature and origin of ultra-high energy (UHE: reffering to > 10^19 eV) cosmic rays are great mysteries in modern astrophysics. The current theories for their explanation include the so-called "top-down" decay scenarios whose main…
At Auger energies only model predictions enable us to extract primary cosmic ray features. The simulation of the shower evolution depends sensitively on the first few interactions, necessarily related to the quality of our understanding of…
The last phase transition predicted by the standard model of particle physics took place at the QCD scale $T\sim200$ MeV when the universe was about $t\sim10^{-5}$ seconds old and the Hubble radius was around 10 Km. In this paper, we…
In Brane Gas Cosmology (BGC) the initial state of the universe is taken to be small, dense and hot, with all fundamental degrees of freedom near thermal equilibrium. This starting point is in close analogy with the Standard Big Bang (SBB)…
The energy spectrum of ultra-high energy cosmic rays (UHECRs) provides essential information on the most energetic phenomena in the Universe. Beyond EeV energies, the Telescope Array and Pierre Auger Observatory have the largest exposures…
It is shown that Eddington-like accretion event in the Galactic center several million years ago and particle acceleration at accompanying shocks and jets could explain the observed cosmic ray spectrum at energies above 1 PeV. Cosmic ray…