Constraints on the fraction of primary gamma rays at ultra-high energies from the muon data of the Yakutsk EAS array |
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Authors: | A V Glushkov D S Gorbunov I T Makarov M I Pravdin G I Rubtsov I E Sleptsov S V Troitsky |
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Institution: | (1) Yakutsk EAS Array Collaboration, Shafer Institute of Cosmophysical Research and Aeronomy, Yakutsk, 677980, Russia;(2) Institute for Nuclear Research, Russian Academy of Sciences, Moscow, 117312, Russia;(3) Faculty of Physics, Moscow State University, Moscow, 119992, Russia |
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Abstract: | By using data on the total signal and on the muon component of air showers detected at the Yakutsk array, the possible upper
limits on the fraction of primary gamma rays at ultra-high energies is analyzed in the framework of the recently suggested
event-by-event approach. Upper limits on the photon fraction in the integral flux of primary cosmic rays are derived. At 95%
C.L., these limits are 22% for primary energies E
0 > 4 × 1019 eV and 12% for E
0 > 2 × 1019 eV. Despite the presence of muonless events, the data are consistent with the complete absence of photons at least at 95%
C.L. The sensitivity of the results to systematic uncertainties, in particular to those of the energy determination for nonphoton
primaries, is discussed.
The text was submitted by the authors in English. |
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