Constraining the fraction of primary gamma rays at ultra-high energies from the muon data of the Yakutsk extensive-air-shower array

Abstract

By making use of the data on the total signal and on the muon component of the air showers detected by the Yakutsk array, we analyze, in the frameworks of the recently suggested event-by-event approach, how large the fraction of primary gamma-rays at ultra-high energies can be. We derive upper limits on the photon fraction in the integral flux of primary cosmic rays. At the 95% confidence level (CL), these limits are 22% for primary energies E_0>4\cdot 10^{19}eV and 12% for E_0>2\cdot 10^{19}eV. Despite the presence of muonless events, the data are consistent with complete absence of photons at least at 95% CL. The sensitivity of the results to systematic uncertainties, in particular to those of the energy determination for non-photon primaries, is discussed.

arXiv comment5 pages, 2 figures

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• Lorentz Violation for Photons and Ultra-High Energy Cosmic Rays
• Constraints on the diffuse photon flux with energies above $10^{18}$ eV using the surface detector of the Telescope Array experiment
• Muon content of ultra-high-energy air showers: Yakutsk data versus simulations
• Upper limit on the flux of photons with energies above 10^19 eV using the Telescope Array surface detector
• Constraints on the flux of primary cosmic-ray photons at energies E > 10^18 eV from Yakutsk muon data
• Cosmic Ray Astronomy
• Sensitivity of cosmic-ray experiments to ultra-high-energy photons: reconstruction of the spectrum and limits on the superheavy dark matter
• Prospective constraints on Lorentz violation from ultrahigh-energy photon detection
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• GZK Photons in the Minimal Ultra High Energy Cosmic Rays Model
• Global anisotropy of arrival directions of ultra-high-energy cosmic rays: capabilities of space-based detectors
• Non-Universal Spectra of Ultra-High Energy Cosmic Ray Primaries and Secondaries in a Structured Universe
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• Double Pair Production by Ultra High Energy Cosmic Ray Photons
• Review of the Multimessenger Working Group at UHECR-2012
• Search for point sources of ultra-high energy photons with the Telescope Array surface detector
• Upper limits on the isotropic diffuse flux of cosmic PeV photons from Carpet-2 observations