Energy determination in the Akeno Giant Air Shower Array experiment

Sep, 2002
28 pages
Published in:
  • Astropart.Phys. 19 (2003) 447-462
e-Print:

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Abstract: (arXiv)
Using data from more than ten-years of observations with the Akeno Giant Air Shower Array (AGASA), we published a result that the energy spectrum of ultra-high energy cosmic rays extends beyond the cutoff energy predicted by Greisen, and Zatsepin and Kuzmin. In this paper, we reevaluate the energy determination method used for AGASA events with respect to the lateral distribution of shower particles, their attenuation with zenith angle, shower front structure, delayed particles observed far from the core and other factors. The currently assigned energies of AGASA events have an accuracy of ±\pm25% in event-reconstruction resolution and ±\pm18% in systematic errors around 1020^{20}eV. This systematic uncertainty is independent of primary energy above 1019^{19}eV. Based on the energy spectrum from 1014.5^{14.5}eV to a few times 1020^{20}eV determined at Akeno, there are surely events above 1020^{20}eV and the energy spectrum extends up to a few times 1020^{20}eV without a GZK-cutoff.
  • cosmic radiation: energy spectrum
  • showers: air
  • showers: spatial distribution
  • time dependence
  • GZK effect
  • data analysis method
  • scintillation counter: plastics
  • shower detector: experimental results