The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform
S A Blake - One of the best experts on this subject based on the ideXlab platform.
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measurement of the flux of ultra high energy cosmic rays by the stereo technique
Astroparticle Physics, 2009Co-Authors: R Abbasi, T Abuzayyad, M Allen, G Archbold, K Belov, J W Belz, D R Bergman, M Alseady, J F Amann, S A BlakeAbstract:The High Resolution Fly’s Eye (HiRes) experiment has measured the flux of ultrahigh energy cosmic rays using the stereoscopic air fluorescence technique. The HiRes experiment consists of two detectors that observe cosmic ray showers via the fluorescence light they emit. HiRes data can be analyzed in monocular mode, where each detector is treated separately, or in stereoscopic mode where they are considered together. Using the monocular mode the HiRes collaboration measured the cosmic ray spectrum and made the first observation of the Greisen–Zatsepin–Kuzmin cutoff. In this paper we present the cosmic ray spectrum measured by the stereoscopic technique. Good agreement is found with the monocular spectrum in all details.
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first observation of the Greisen zatsepin kuzmin suppression
Physical Review Letters, 2008Co-Authors: R Abbasi, T Abuzayyad, M Allen, J F Amman, G Archbold, K Belov, J W Belz, S Ben Y Zvi, D R Bergman, S A BlakeAbstract:The High Resolution Fly's Eye (HiRes) experiment has observed the Greisen-Zatsepin-Kuzmin suppression (called the GZK cutoff) with a statistical significance of five standard deviations. HiRes' measurement of the flux of ultrahigh energy cosmic rays shows a sharp suppression at an energy of $6\ifmmode\times\else\texttimes\fi{}{10}^{19}\text{ }\text{ }\mathrm{eV}$, consistent with the expected cutoff energy. We observe the ankle of the cosmic-ray energy spectrum as well, at an energy of $4\ifmmode\times\else\texttimes\fi{}{10}^{18}\text{ }\text{ }\mathrm{eV}$. We describe the experiment, data collection, and analysis and estimate the systematic uncertainties. The results are presented and the calculation of the statistical significance of our observation is described.
V Berezinsky - One of the best experts on this subject based on the ideXlab platform.
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second dip as a signature of ultrahigh energy proton interactions with cosmic microwave background radiation
Physical Review Letters, 2006Co-Authors: V Berezinsky, A Gazizov, M KachelriesAbstract:We discuss as a new signature for the interaction of extragalactic ultrahigh energy protons with cosmic microwave background radiation a spectral feature located at E= 6.3 x 10(19) eV in the form of a narrow and shallow dip. It is produced by the interference of e+e(-)-pair and pion production. We show that this dip and, in particular, its position are almost model-independent. Its observation by future ultrahigh energy cosmic ray detectors may give the conclusive confirmation that an observed steepening of the spectrum is caused by the Greisen-Zatsepin-Kuzmin effect.
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ultrahigh energy cosmic rays without Greisen zatsepin kuzmin cutoff
Physical Review Letters, 1997Co-Authors: V Berezinsky, M Kachelriess, Alexander VilenkinAbstract:We study the decays of metastable superheavy particles as the source of ultrahigh energy cosmic rays (UHE CR). These particles are assumed to constitute a tiny fraction {xi}{sub X} of cold dark matter in the Universe. The UHE CR fluxes produced at the decays of X particles are calculated. The dominant contribution is given by fluxes of photons and nucleons from the halo of our Galaxy and thus does not exhibit the GZK cutoff. The extragalactic components of UHE CR are suppressed by the smaller extragalactic density of X particles and, hence, the cascade limit is relaxed. We discuss the spectrum of produced extensive air showers and a signal from a Virgo cluster as signatures of this model. {copyright} {ital 1997} {ital The American Physical Society}
R Abbasi - One of the best experts on this subject based on the ideXlab platform.
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measurement of the flux of ultra high energy cosmic rays by the stereo technique
Astroparticle Physics, 2009Co-Authors: R Abbasi, T Abuzayyad, M Allen, G Archbold, K Belov, J W Belz, D R Bergman, M Alseady, J F Amann, S A BlakeAbstract:The High Resolution Fly’s Eye (HiRes) experiment has measured the flux of ultrahigh energy cosmic rays using the stereoscopic air fluorescence technique. The HiRes experiment consists of two detectors that observe cosmic ray showers via the fluorescence light they emit. HiRes data can be analyzed in monocular mode, where each detector is treated separately, or in stereoscopic mode where they are considered together. Using the monocular mode the HiRes collaboration measured the cosmic ray spectrum and made the first observation of the Greisen–Zatsepin–Kuzmin cutoff. In this paper we present the cosmic ray spectrum measured by the stereoscopic technique. Good agreement is found with the monocular spectrum in all details.
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first observation of the Greisen zatsepin kuzmin suppression
Physical Review Letters, 2008Co-Authors: R Abbasi, T Abuzayyad, M Allen, J F Amman, G Archbold, K Belov, J W Belz, S Ben Y Zvi, D R Bergman, S A BlakeAbstract:The High Resolution Fly's Eye (HiRes) experiment has observed the Greisen-Zatsepin-Kuzmin suppression (called the GZK cutoff) with a statistical significance of five standard deviations. HiRes' measurement of the flux of ultrahigh energy cosmic rays shows a sharp suppression at an energy of $6\ifmmode\times\else\texttimes\fi{}{10}^{19}\text{ }\text{ }\mathrm{eV}$, consistent with the expected cutoff energy. We observe the ankle of the cosmic-ray energy spectrum as well, at an energy of $4\ifmmode\times\else\texttimes\fi{}{10}^{18}\text{ }\text{ }\mathrm{eV}$. We describe the experiment, data collection, and analysis and estimate the systematic uncertainties. The results are presented and the calculation of the statistical significance of our observation is described.
A A Watson - One of the best experts on this subject based on the ideXlab platform.
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high energy cosmic rays and the Greisen zatsepin kuz min effect
Reports on Progress in Physics, 2014Co-Authors: A A WatsonAbstract:Although cosmic rays were discovered over 100 years ago their origin remains uncertain. They have an energy spectrum that extends from ∼1 GeV to beyond 1020 eV, where the rate is less than 1 particle per km2 per century. Shortly after the discovery of the cosmic microwave background in 1965, it was pointed out that the spectrum of cosmic rays should steepen fairly abruptly above about 4 × 1019 eV, provided the sources are distributed uniformly throughout the Universe. This prediction, by Greisen and by Zatsepin and Kuz'min, has become known as the GZK effect and in this article I discuss the current position with regard to experimental data on the energy spectrum of the highest cosmic-ray energies that have been accumulated in a search that has lasted nearly 50 years. Although there is now little doubt that a suppression of the spectrum exists near the energy predicted, it is by no means certain that this is a manifestation of the GZK effect as it might be that this energy is also close to the maximum to which sources can accelerate particles, with the highest energy beam containing a large fraction of nuclei heavier than protons. The way forward is briefly mentioned.
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high energy cosmic rays and the Greisen zatsepin kuzmin effect
arXiv: High Energy Astrophysical Phenomena, 2013Co-Authors: A A WatsonAbstract:Although cosmic rays were discovered over 100 years ago their origin remains uncertain. They have an energy spectrum that extends from 1 GeV to beyond 1020 eV, where the rate is less than 1 particle per km2 per century. Shortly after the discovery of the cosmic microwave background in 1965, it was pointed out that the spectrum of cosmic rays should steepen fairly abruptly above about 4 x 1019 eV, provided the sources are distributed uniformly throughout the Universe. This prediction, by Greisen and by Zatsepin and Kuzmin, has become known as the GZK-effect and in this article I discuss the current position with regard to experimental data on the energy spectrum of the highest cosmic-ray energies that have been accumulated in a search that has lasted nearly 50 years. Although there is now little doubt that a suppression of the spectrum exists near the energy predicted, it is by no means certain that this is a manifestation of the GZK-effect as it might be that this energy is also close to the maximum to which sources can accelerate particles, with the highest-energy beam containing a large fraction of nuclei heavier than protons. The way forward is briefly mentioned.
Jonas Moller Larsen - One of the best experts on this subject based on the ideXlab platform.
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strangelets as cosmic rays beyond the Greisen zatsepin kuzmin cutoff
Physical Review Letters, 2003Co-Authors: Jes Madsen, Jonas Moller LarsenAbstract:Strangelets (stable lumps of quark matter) can have masses and charges much higher than those of nuclei, but have very low charge-to-mass ratios. This is confirmed in a relativistic Thomas-Fermi model. The high charge allows astrophysical strangelet acceleration to energies orders of magnitude higher than for protons. In addition, strangelets are much less susceptible to the interactions with the cosmic microwave background that suppress the flux of cosmic ray protons and nuclei above energies of 10(19)-10(20) eV (the Greisen-Zatsepin-Kuzmin cutoff). This makes strangelets an interesting possibility for explaining ultrahigh energy cosmic rays.
