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Extension of the Cosmic-Ray Energy Spectrum Beyond the Predicted Greisen-Zatsepin-Kuz'min Cutoff

M. Takeda, N. Hayashida, K. Honda, N. Inoue, K. Kadota, F. Kakimoto, K. Kamata, S. Kawaguchi, Y. Kawasaki, N. Kawasumi, H. Kitamura, E. Kusano, Y. Matsubara, K. Murakami, M. Nagano, D. Nishikawa, H. Ohoka, N. Sakaki, M. Sasaki, K. Shinozaki, N. Souma, M. Teshima, R. Torii, I. Tsushima, Y. Uchihori, T. Yamamoto, S. Yoshida, H. Yoshii

astro-pharXiv:astro-ph/9807193

Abstract

The cosmic-ray energy spectrum above 1018.5 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 1020 eV and the energy gap between the highest energy event and the others is being filled up with recently observed events. The spectral shape suggests the absence of the 2.7 K cutoff in the energy spectrum or a possible presence of a new component beyond the 2.7 K cutoff.

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