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arXiv · 1307.4988

Estimate of the fraction of primary photons in the cosmic-ray flux at energies ~10^17 eV from the EAS-MSU experiment data

Yu. A. Fomin·N. N. Kalmykov·G. V. Kulikov·V. P. Sulakov·S. V. Troitsky
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Abstract

We reanalyze archival EAS-MSU data in order to search for events with anomalously low content of muons with energies E_mu>10 GeV in extensive air showers with number of particles N_e>2*10^7. We confirm the first evidence for nonzero flux of primary cosmic gamma rays at energies E~10^17 eV. The estimated fraction of primary gamma rays in the flux of cosmic particles with energies E>5.4*10^16 eV is (0.43 +0.12-0.11)%, which corresponds to the intensity of (1.2 +0.4-0.3)*10^{-16} cm^{-2} s^{-1} sr^{-1}. The study of arrival directions does not favour any particular mechanism of the origin of the photon-like events.

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Yu. A. Fomin, N. N. Kalmykov, G. V. Kulikov, V. P. Sulakov, S. V. Troitsky. 2013-11-11. Estimate of the fraction of primary photons in the cosmic-ray flux at energies ~10^17 eV from the EAS-MSU experiment data. https://doi.org/10.1134/s1063776113140112%2010.7868%2Fs0044451013120043

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