Related papers: The transition from galactic to extragalactic cosm…
We discuss recent models in which neutrinos, which are assumed to have mass in the eV range, originate the highest energy cosmic rays by interaction with the enhanced density in the galactic halo of the relic cosmic neutrino background. We…
We estimate energy spectra and fluxes at the Earth's surface of the cosmic and Galactic neutrino backgrounds produced by thermonuclear reactions in stars. The extra-galactic component is obtained by combining the most recent estimates of…
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…
This paper summarizes recent developments in the study of the propagation of ultra-high energy cosmic ray protons or nuclei in the Universe, with emphasis on the consequences of energy losses and on the influence of extra-galactic magnetic…
Cosmic rays have been observed up to energies $10^8$ times larger than those of the best particle accelerators. Studies of astrophysical particles (hadrons, neutrinos and photons) at their highest observed energies have implications for…
A flux of extra-terrestrial neutrinos at energies $\gg10^{15}$ eV has the potential to serve as a cosmological probe of the high-energy universe as well as tests of fundamental particle interactions. Cosmogenic neutrinos, produced from the…
We compute the ultra-high energy cosmic ray horizon, i.e. the distance up to which cosmic ray sources may significantly contribute to the fluxes above a certain threshold on the observed energies. We obtain results both for proton and heavy…
The energy spectrum, composition and arrival directions of ultrahigh energy cosmic rays (UHECRs) with energy above the cosmic ray ankle, measured by the Pierre Auger Observatory, are inconsistent if their origin is assumed to be…
We explore scenarios where the highest energy cosmic rays are produced by new particle physics near the grand unification scale. Using detailed numerical simulations of extragalactic nucleon, gamma-ray, and neutrino propagation, we show the…
We consider the propagation of galactic cosmic rays under assumption that the interstellar medium is a fractal one. An anomalous diffusion equation in terms of fractional derivatives is used to describe of cosmic ray propagation. The…
The chemical composition of ultra-high energy cosmic rays is a key question in particle astrophysics. The measured composition, inferred from the elongation rates of cosmic ray showers, looks in general very different from the initial…
High energy neutrino astrophysics has come of age with the discovery by IceCube of neutrinos in the TeV to PeV energy range attributable to extragalactic sources at cosmological distances. At such energies, astrophysical neutrinos must have…
Our knowledge of the high-energy universe is undergoing a period of rapid change as new astronomical detectors of high-energy radiation start to operate at their design sensitivities. Now is a boomtime for high-energy astrophysics, with new…
It has long been recognized that magnetic fields play an important role in many astrophysical environments, yet the strength and structure of magnetic fields beyond our solar system have been at best only qualitatively constrained. The…
We discuss the production of cosmogenic neutrinos on extragalactic infrared photons in a model of its cosmological evolution. The relative importance of these infrared photons as a target for proton interactions is significant, especially…
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…
We present a brief introduction to the physics of Ultra High Energy Cosmic Rays (UHECRs), concentrating on the experimental results obtained so far and on what, from these results, can be inferred about the sources of UHECRs.
Ultra-high energy cosmic rays are mostly charged particles and they are therefore deflected by magnetic fields on their path from their sources to Earth. An interesting phenomenon arising from these deflections is the appearance of multiple…
We have developed a model which aims to reproduce observational data of many kinds related to cosmic-ray origin and propagation: direct measurements of nuclei, antiprotons, electrons and positrons, gamma-rays, and synchrotron radiation. Our…
We study spectra of the Ultra High Energy Cosmic Rays assuming primaries are protons and photons, and that their sources are extragalactic. We assume power low for the injection spectra and take into account the influence of cosmic…