Related papers: Final Results from the High Resolution Fly's Eye (…
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 present the results of searches for correlation between ultra--high-energy cosmic rays observed in stereo mode by the High Resolution Fly's Eye (HiRes) experiment and objects of the BL Lac subclass of active galaxies. In particular, we…
High energy cosmic rays allow probing phenomena that are inacessible to accelerators. Observation of cosmic rays, presumebly protons, with energies beyond $4 \times 10^{19} eV$, the so-called Greisen-Zatsepin-Kuzmin (GZK) cut-off, give…
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…
The detection of the GZK feature in the cosmic ray spectrum, resultingfrom the production of pions by ultra-high energy protons scattering off the cosmic microwave background (CMB), can shed light on the mysterious sources of these high…
The spectrum of extra-galactic cosmic rays (CRs) is expected to follow the Greisen-Zatsepin-Kuzmin (GZK) cutoff at about 5x10^10 GeV which results from energy losses of charged nuclei in the cosmic microwave background. So far the…
Cosmic rays with energies above $10^{19}$ eV, observed in 1999-2004 by the High Resolution Fly's Eye (HiRes) experiment in the stereoscopic mode, were found to correlate with directions to distant BL Lac type objects (BL Lacs), suggesting…
Observations of cosmic rays with energies above ~ 4 x 10^{10} GeV have inspired several speculative suggestions concerning their origin. The crucial question is whether or not the spectrum exhibits the expected `GZK cutoff' at this energy…
The field of ultra-high energy cosmic rays made a lot of progresses last years with large area experiments such as the Pierre Auger Observatory, HiRes and the Telescope Array. A suppression of the cosmic ray flux at energies above…
Ultra-high-energy (UHE) cosmic rays (CRs) interact with cosmic background radiation through hadronic processes, and the Universe would become `opaque' to UHE CRs of energies $\sim$($10^{18}$- $10^{20}$) eV over about several tens of Mpc,…
We present studies of systematic uncertainties in the measurement of the ultra-high energy cosmic ray (UHECR) spectrum with the FADC detector of the High Resolution Fly's Eye experiment (HiRes-II). One source of uncertainties lies in the…
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…
It is not yet clear whether the observed flux suppression for ultra-high energy cosmic rays (UHECR) at energies above \simeq 4.10E19 eV is a signature of the Greisen-Zatsepin-Kuzmin (GZK) cutoff or corresponds, for instance, to the maximum…
We present the results of a search for small-scale anisotropy in the distribution of arrival directions of cosmic rays above 10^19 eV measured in stereo by the High Resolution Fly's Eye (HiRes) experiment. Performing an autocorrelation scan…
We fit the HiRes ultra-high energy cosmic ray (UHECR) spectrum measurements with broken power laws in order to identify features. These fits find the previously observed feature known as the Ankle at 10**18.5 eV, as well as evidence for a…
This is an introductory review about the on-going search for a signal of Lorentz Invariance Violation (LIV) in cosmic rays. We first summarise basic aspects of cosmic rays, focusing on rays of ultra high energy (UHECRs). We discuss the…
We investigate the possibility that cosmic rays of energy larger than the Greisen-Zatsepin-Kuzmin cutoff are not nucleons, but a new stable, massive, hadron that appears in many extensions of the standard model. We focus primarily on the…
We have searched for correlations between the pointing directions of ultrahigh energy cosmic rays observed by the High Resolution Fly's Eye experiment and Active Galactic Nuclei (AGN) visible from its northern hemisphere location. No…
We give an outline of possible extragalactic explanations of the highest energy cosmic ray events. We give a classification of the possible particles which could have caused the events and try to find suitable sources for each class. In…
The status of the observations of Ultra High Energy Cosmic Rays will be reviewed, focusing on the the latest results of HiRes and Auger observatories. A comprehensive analytical computation scheme to compute the expected UHECR spectrum on…