Observation of the GZK Cutoff by the HiRes Experiment
G.B. Thomson (for the High Resolution Fly's Eye (HiRes) Collaboration)
TL;DR
The HiRes experiment provides strong evidence for the GZK cutoff in cosmic ray flux at around 6 x 10^{19} eV, confirming a key prediction of cosmic ray physics with a five sigma significance.
Contribution
This work presents the first high-confidence observation of the GZK cutoff using the HiRes detector, confirming theoretical predictions about cosmic ray suppression at ultra-high energies.
Findings
Sharp flux suppression at 6 x 10^{19} eV consistent with GZK cutoff
Detection of the cosmic ray spectrum ankle at 4 x 10^{18} eV
Five standard deviation significance of the GZK cutoff observation
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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Taxonomy
TopicsAstrophysics and Cosmic Phenomena · Particle Detector Development and Performance · Dark Matter and Cosmic Phenomena