相关论文: Extremely high energy cosmic rays from relic parti…
The neutron fraction in the very high energy cosmic rays near the Greisen-Zatsepin-Kuzmin (GZK) cutoff energy is analyzed by taking into account the time dilation effect of the neutron decays and also the pion photoproduction behaviors…
Transrelativistic supernovae (SNe), which are likely driven by central engines via jets or winds, have been among candidate sources of ultrahigh-energy cosmic rays (UHECRs). We investigate acceleration and survival of UHECR nuclei in the…
We argue that if ultrahigh-energy (E > 10^10 GeV) cosmic rays are heavy nuclei (as indicated by existing data), then the pointing of cosmic rays to their nearest extragalactic sources is expected for 10^10.6 < E/GeV < 10^11. This is because…
We calculate the spectrum of ultra high energy cosmic rays produced by the decay of a superheavy dark matter population clustered in the galactic halo. To perform this calculation we start with fragmentation functions measured at LEP and…
In this thesis, I describe in great detail the physics of the decay of any Super-Heavy X particle (with masses up to the grand unification scale ~ 10^16 GeV and possibly beyond), and the computer code I developed to model this process -…
Analytical calculations of extra-galactic cosmic ray spectra above ~10^17 eV are often performed assuming continuous source distributions, giving rise to spectra that depend little on the propagation mode, be it rectilinear or diffusive. We…
Simple arguments concerning power and acceleration efficiency show that ultra-high energy cosmic rays (UHECRS) with energies >~ 10^{19} eV could originate from GRBs. Neutrons formed through photo-pion production processes in GRB blast waves…
``Top--down'' models explain the observation of ultra high energy cosmic rays (UHECR; $E \gsim 5 \cdot 10^{19}$ eV) through the decay of very massive, long--lived ``$X$ particles''. If superparticles with masses near a TeV exist, $X$ decays…
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…
Observation of Ultra High Energy Cosmic Rays (UHECR) -whose energy exceeds $10^20$eV- is still a puzzle for modern astrophysics. The transfer of more than 16 Joules to a microscopic particle can hardly be achieved, even in the most powerful…
We revisit constraints on decaying very heavy dark matter (VHDM) using the latest ultrahigh-energy cosmic-ray (UHECR; $E\gtrsim 10^{18}$ eV) data and ultrahigh-energy (UHE) $\gamma$-ray flux upper limits, measured by the Pierre Auger…
Dark matter particles could be superheavy, provided their lifetime is much longer than the age of the universe. Using the sensitivity of the Pierre Auger Observatory to ultra-high energy neutrinos and photons, we constrain a specific…
While several arguments can be proposed against the existence of particles with energy in excess of $(3-5)\times 10^{19}$ eV in the cosmic ray spectrum, these particles are actually observed and their origin seeks for an explanation. After…
The recently observed ultra-high energy (UHE) cosmic rays beyond the Greisen-Zatsepin-Kuzmin bound can be explained by the decays of some superheavy $X$ particles forming a part of dark matter in our universe. We consider various discrete…
We analyze the spectrum of the ultrahigh energy (above \approx 10^{9} GeV) cosmic rays. With a maximum likelihood analysis we show that the observed spectrum is consistent with the decay of extragalactic GUT scale particles. The predicted…
Special relativity has been tested at low energy with great accuracy, but its extrapolation to very high-energy phenomena is much less well established. Introducing a critical distance scale, a , below 10E-25 cm (the wavelength scale of the…
We argue that the superheavy gravitinos that we had previously proposed as candidates for Dark Matter can offer a possible explanation for the ultra-high energy cosmic ray (UHECR) events observed at the Pierre Auger Observatory, via…
Neutrinos from far away sources annihilating at the Z resonance on relic neutrinos may give origin to the ultrahigh-energy cosmic rays. Here we present predictions of this mechanism with relic neutrinos lighter than 1 eV, which do not…
Since neutrinos have mass differences, they could decay into one another. But their lifetimes are likely long, even when shortened by new physics, so decay likely impacts neutrinos only during long trips. This makes high-energy…
We discuss the production of ultra high energy secondary protons by cosmic ray primary nuclei propagating in the intergalactic space through Cosmic Microwave Background (CMB) and Infrared (IR) radiations. Under the assumption that only…