相关论文: Electroweak instantons as a solution to the ultrah…
We show that all features of the ultrahigh energy cosmic ray spectrum from 10^{17} eV to 10^{21} eV can be described with a simple power-like injection spectrum of protons under the assumption that the neutrino-nucleon cross-section is…
After a short review of the ultrahigh energy cosmic ray puzzle - the apparent observation of cosmic rays originating from cosmological distances with energies above the expected Greisen-Zatsepin-Kuzmin cutoff 4x10^{19} eV - we consider…
In a recently proposed model the cosmic rays spectrum at energies above 10^{18} eV can be fitted with a minimal number of unknown parameters assuming that the extragalactic cosmic rays are only protons with a power law source spectrum…
The IceCube experiment recently detected the first flux of high-energy neutrinos in excess of atmospheric backgrounds. We examine whether these neutrinos originate from within the same extragalactic sources as ultrahigh-energy cosmic rays.…
Despite 100 years of effort, we still know very little about the origin of ultra-high energy cosmic rays. The observation of neutrinos produced when cosmic-ray protons with energies above $4\times 10^{19}$ eV interact with the cosmic…
The origin and composition of ultra-high-energy cosmic rays (UHECRs) remain a mystery. The proton dip model describes their spectral shape in the energy range above $10^9$ GeV by pair production and photohadronic interactions with the…
The observation of twenty cosmic-ray air-showers at and above 10^{20} eV poses fascinating problems for particle astrophysics: how the primary particles are accelerated to these energies, how the primaries get here through the 2.7K…
Protons with energies up to 10^15 eV are the main component[1] of cosmic rays, but evidence for the specific locations where they could have been accelerated to these energies has been lacking[2]. Electrons are known to be accelerated to…
Scattering processes in the cosmic microwave background limit the propagation of ultra high energy charged particles in our Universe. For extragalactic proton sources resonant photopion production results in the famous…
It has been suggested that the characteristic energy of string models may be considerably lower than the observed Planck mass. In such schemes, the unification of interactions takes place around the string scale, perhaps as low as a few…
We discuss the GZK horizon of protons and present a method to constrain the injection spectrum of ultrahigh energy cosmic rays (UHECRs) from supposedly identified extragalactic sources. This method can be applied even when only one or two…
In this report we review the important progress made in recent years towards understanding the experimental data on ultra-high-energy ($E \gtrsim 10^9$ GeV) cosmic rays. We begin with a general survey of the available data, including a…
In this paper we briefly discuss the problem of the origin of Ultra High Energy Cosmic Rays in the framework of Top-Down models. We show that, for high energy of decays and in a wide range of spectra of injected protons, their extragalactic…
Resonant photopion production with the cosmic microwave background predicts a suppression of extragalactic protons above the famous Greisen-Zatsepin-Kuzmin cutoff at about E_{GZK} ~ 5 x 10^10 GeV. Current cosmic ray data measured by the…
Cosmogenic neutrinos are produced when ultra-high-energy cosmic rays (UHECRs) interact with cosmological photon fields. Limits on the diffuse flux of these neutrinos can be used to constrain the fraction of protons arriving at Earth with…
We investigate the injection spectrum of ultra-high-energy (>10^{15} eV) cosmic rays under the hypotheses that (1) these cosmic rays are protons and (2) the sources of these cosmic rays are extra-galactic and are homogeneously distributed…
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…
Ultra-high energy cosmic ray (UHECR) protons produced by uniformly distributed astrophysical sources contradict the energy spectrum measured by both the AGASA and HiRes experiments, assuming the small scale clustering of UHECR observed by…
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…
The properties of cosmic rays with energies above 10**6 GeV have to be deduced from the spacetime structure and particle content of the air showers which they initiate. In this review we summarize the phenomenology of these giant air…