Upper limit on the cosmic-ray photon fraction at EeV energies from the Pierre Auger Observatory

By The Pierre Auger Collaboration J. Abraham, P. Abreu, M. Aglietta, C. Aguirre, E. Ahn, D. Allard, I. Allekotte, J. Allen, P. Allison, J. Álvarez-Muñiz and 450 more. 2009

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From direct observations of the longitudinal development of ultra-high energy air showers performed with the Pierre Auger Observatory, upper limits of 3.8%, 2.4%, 3.5% and 11.7% (at 95% c.l.) are obtained on the fraction of cosmic-ray photons above 2, 3, 5 and 10 EeV (1 EeV = 10^18 eV) respectively. These are the first experimental limits on ultra-high energy photons at energies below 10 EeV. The results complement previous constraints on top-down models from array data and they reduce systematic uncertainties in the interpretation of shower data in terms of primary flux, nuclear composition and proton-air cross-section.

Subfields: Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/104454c06b2b0c15d4017bdb24f1c176b9b048e3

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Citations in the corpus

• The Astrophysics of Ultrahigh-Energy Cosmic Rays (2011, background): “The differential limit and the integral flux limit on a pure E−2 spectrum (straight line) are presented for IceCube 22 lines (pale blue, Abbasi et al. 2010), ANITA-II (green, Gorham et al. 2010) and Auger South (red, Abraham et al. 2009a).”