Upper limit on the ultra-high-energy photon flux from AGASA and Yakutsk data

We present the interpretation of the muon and scintillation signals of ultra-high-energy air showers observed by AGASA and Yakutsk extensive air shower array experiments. We consider case-by-case ten highest energy events with known muon content and conclude that at the 95% confidence level (C.L.) n...

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Bibliographic Details
Main Authors: Rubtsov, G I, Dedenko, L G, Fedorova, G F, Fedunin, E Y, Glushkov, A V, Gorbunov, D S, Makarov, I T, Pravdin, M I, Roganova, T M, Sleptsov, I E, Troitsky, S V
Language:English
Published: 2006
Subjects:
Astrophysics and Astronomy
Yakutsk
Online Access:http://cds.cern.ch/record/923285
Description
Summary:We present the interpretation of the muon and scintillation signals of ultra-high-energy air showers observed by AGASA and Yakutsk extensive air shower array experiments. We consider case-by-case ten highest energy events with known muon content and conclude that at the 95% confidence level (C.L.) none of them was induced by a primary photon. Taking into account statistical fluctuations and differences in the energy estimation of proton and photon primaries, we derive an upper limit of 36% at 95% C.L. on the fraction of primary photons in the cosmic-ray flux above 10^20 eV. This result disfavors the Z-burst and superheavy dark-matter solutions to the GZK-cutoff problem.

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