Upper limit on the primary photon fraction from the Pierre Auger Observatory

THE PIERRE AUGER COLLABORATION (AUTOR 384 DE 427); M. J. TUEROS

Pune, India

Conferencia; 29th International Cosmic Ray Conference; 2005

Tata Institute of Fundamental Research

Based on observations of the depth of shower maximum performed with the hybrid detector of the Auger Observatory, an upper limit on the cosmic-ray photon fraction of 26% (at 95% confidence level) is derived for primary energies above 1E19 eV. Additional observables recorded with the surface detector array, available for a sub-set of the data sample, support the conclusion that a photon origin of the observed events is not favoured.