Related papers: Ultra High Energy Cosmic Rays: Observations and Th…
Regarding ultrahigh-energy cosmic rays (UHECRs) as a probe and extra dimensions as a possible ingredient of the fantastic ultrahigh-energy world, we discuss possible interplay between them. On the one hand small extra dimensions and…
The origin of ultra-high energy cosmic rays (UHECRs) has been an open question for decades. Here, we use a combination of hydrodynamic simulations and general physical arguments to demonstrate that UHECRs can in principle be produced by…
The paper describes methods used for the detection of cosmic rays with energies above 10^18 eV (UHECR, UltraHigh Energy Cosmic Rays). It had been anticipated there would be a cutoff in the energy spectrum of primary cosmic rays around 3…
Ultra High Energy Cosmic Rays (UHECRs) interact en route to Earth, producing secondary gamma-rays. For the case of high cosmic ray power and weak intergalactic magnetic fields, the deflections of these UHECRs may be small leading to…
We describe the current situation of the data on the highest energy particles in the Universe - the ultrahigh energy cosmic rays. The new results in the field come from the Telescope Array experiment in Utah, U.S.A. For this reason we…
Ultra high energy cosmic rays (UHECR) pose a problem either for particle physics or for astrophysics (or for both) by the unexpectedly high number of cosmic ray showers observed with energy above about 5x10^{19}eV, the…
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.…
High energy Astroparticles include Cosmic Ray, gamma ray and neutrinos, all of them coming from the universe. The origin and production, acceleration and propagation mechanisms of ultrahigh-energy CR (up to $10^{20}$ eV) are still unknown.…
The origin of ultra-high energy cosmic rays (UHECRs) is one of the enduring mysteries of high-energy astrophysics. To investigate this, we cross-correlate the recently released Fermi Large Area Telescope First Source Catalog (1FGL) with the…
The origin of ultra-high-energy cosmic rays (UHECRs) remains an open questions in astrophysics. We explore two primary scenarios for the distribution of UHECR sources, assuming that their production rate follows either the cosmic…
Observation of clustering of ultra-high energy cosmic rays (UHECR) suggests that they are emitted by compact sources. Assuming small deflection of UHECR during the propagation, the statistical analysis of clustering allows to estimate the…
In this paper we review the extragalactic propagation of ultrahigh energy cosmic-rays (UHECR). We present the different energy loss processes of protons and nuclei, and their expected influence on energy evolution of the UHECR spectrum and…
In this review we discuss the important progress made in recent years towards understanding the experimental data on cosmic rays with energies $\agt 10^{19}$ eV. We begin with a brief survey of the available data, including a description of…
The current status of the theory of particle acceleration at relativistic shocks is presented, and a few possible scenarios for ultra-high-energy cosmic ray production at such shocks are briefly discussed.
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 energy losses and spectra of Ultra High Energy Cosmic Rays (UHECR) are calculated for protons as primary particles. The attention is given to the energy losses due to electron-positron production in collisions with the microwave 2.73 K…
If gamma-ray bursts are sources of ultra-high energy cosmic rays, then radiative signatures of hadronic acceleration are expected in GRB data. Observations with the Fermi Gamma-ray Space Telescope offer the best means to search for evidence…
We explore scenarios where the highest energy cosmic rays (HECR) are produced by new particle physics near the grand unification scale. Using detailed numerical simulations of extragalactic cosmic and gamma-ray propagation, we show the…
We investigate whether ultra--high energy cosmic rays (UHECR) may be preferentially produced in massive galaxy clusters, by looking for correlations between UHECR directions and those of x-ray clusters. We find an excess-above-random of…
The sources of ultra-high energy cosmic rays (UHECRs) are still one of the main open questions in high-energy astrophysics. If UHECRs are accelerated in astrophysical sources, they are expected to produce high-energy photons and neutrinos…