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Observation of the GZK Cutoff by the HiRes Experiment

G. B. Thomson
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Abstract

The High Resolution Fly's Eye (HiRes) experiment has observed the GZK cutoff. HiRes' measurement of the flux of cosmic rays shows a sharp suppression at an energy of 6 x 10^{19} eV, exactly the expected cutoff energy. We observe the ``ankle'' of the cosmic ray spectrum as well, at an energy of 4 x 10^{18} eV. We describe the experiment, data collection, analysis, and estimate the systematic uncertainties. The results are presented and the calculation of a five standard deviation observation of the GZK cutoff is described.

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G. B. Thomson. 2006-09-14. Observation of the GZK Cutoff by the HiRes Experiment. https://arxiv.org/abs/astro-ph/0609403

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