Related papers: Final Results from the High Resolution Fly's Eye (…
The origin and nature of ultrahigh-energy cosmic ray events, above the Greisen-Zatsepin-Kuzmin (GZK) cutoff energy, constitute a long-standing, unsolved mistery. Neutrinos are proposed candidates but their standard interactions with matter…
The search for the origin of cosmic rays is a quest of almost a hundred years. A recent theoretical proposal gives quantitative predictions, which can be tested with data. Specifically, it has been suggested, that all cosmic rays can be…
The maximum distance bound for ultrahigh energy cosmic rays (UHECR) with energies above the Greisen-Zatsepin-Kuzmich cutoff $\sim 10^{19} eV$ relaxes significantly if there is some mechanism that forces UHECR to propagate in discrete…
Using the Auger mass-composition analysis of ultra high energy cosmic rays, based on the shape-fitting of $X_{max}$ distributions, we demonstrate that mass composition and energy spectra measured by Auger, Telescope Array and HiRes can be…
We consider the possibility that the ultra-high-energy cosmic ray flux has a small component of exotic particles which create showers much deeper in the atmosphere than ordinary hadronic primaries. It is shown that applying the conventional…
We measure the spectrum of cosmic rays with energies greater than $10^{18.2}$ eV with the Fluorescence Detectors (FDs) and the Surface Detectors (SDs) of the Telescope Array Experiment using the data taken in our first 2.3-year observation…
I summarize in this paper the results and perspectives of representative ground experiments for the observation of very high energy cosmic rays.
Almost half a century ago, Greisen, Zatsepin and Kuz'min (GZK) predicted a "cosmologically meaningful termination" of the spectrum of cosmic rays at energies around $10^{20}$ eV due to their interaction with the cosmic microwave background,…
The cosmic-ray energy spectrum above 10^{18.5} eV is reported using the updated data set of the Akeno Giant Air Shower Array (AGASA) from February 1990 to October 1997. The energy spectrum extends beyond 10^{20} eV and the energy gap…
The H.E.S.S. collaboration continues to run an array of five Imaging Atmospheric Cherenkov Telescopes to observe the Southern sky in very high energy gamma-rays. In this presentation, recent highlight results obtained with H.E.S.S. are…
We have measured the spectrum of UHE cosmic rays in monocular mode using separately both detectors the High Resolution Fly's Eye experiment. We describe the two detectors and the basic methods of analysis, and we present our measured…
String unification at a scale of a few tens of TeV explains the existence of cosmic ray interactions beyond the Greisen-Zatsepin-Kuzmin (GZK) cutoff. Trans-GZK cosmic rays are neutrinos which can penetrate the cosmic microwave background.…
Although cosmic rays were discovered 90 years ago, we do not know how and where they are accelerated. There is compelling evidence that the highest energy cosmic rays are extra-galactic -- they cannot be contained by our galaxy's magnetic…
The properties of strangelets are reviewed and two experiments searching for them in cosmic rays are described. The prospects for strangelets as ultra-high energy cosmic rays beyond the classical GZK-cutoff are discussed.
Galaxies at high redshifts provide a valuable tool to study cosmic dawn, and therefore it is crucial to reliably identify these galaxies. Here, we present an unambiguous and first simultaneous detection of both the Lyman-alpha emission and…
There has been much interest in possible violations of Lorentz invariance, particularly motivated by quantum gravity theories. It has been suggested that a small amount of Lorentz invariance violation (LIV) could turn off photomeson…
We review some of the recent progress in our knowledge about high-energy cosmic rays, with an emphasis on the interpretation of the different observational results. We discuss the effects that are relevant to shape the cosmic ray spectrum…
Recent advances in measuring and interpreting cosmic rays from the spectral ankle to the highest energies are briefly reviewed. The prime question at the highest energies is about the origin of the flux suppression observed at E ~ 4x10^{19}…
The whole spectrum of high-energy cosmic ray (HECR) is, very likely, influenced by tachyonic neutrinos. Especially, the appearance of two knees can be fitted by the tachyon mass $m(\nu_e)=m(\nu_\mu)\simeq 0.51$ eV/$c^2$ as predicted by a…
We compare the expected contribution of FR-II hot spots to the ultra-high energy cosmic ray spectrum (Rachen & Biermann 1993, A&A in press, BB paper astro-ph/9301010) to improved experimental results. We introduce a "world data set" of UHE…