Title

An upper limit to the photon fraction in cosmic rays above 10 < sup> 19 eV from the Pierre Auger Observatory

Authors

J. Abraham, Karlsruhe Institute of Technology, Campus South
M. Aglietta, Louisiana State University
C. Aguirre, National Technical University of Athens
D. Allard, Charles University
I. Allekotte, Consejo Nacional de Investigaciones Científicas y Técnicas
P. Allison, Universidade Estadual do Sudoeste da Bahia
C. Alvarez, The Ohio State University
J. Alvarez-Muñiz, Pierre Auger Observatory
M. Ambrosio, Colorado State University
L. Anchordoqui, Universidade Estadual de Feira de Santana
J. C. Anjos, Università degli Studi dell'Aquila
C. Aramo, Colorado State University
K. Arisaka, Universidade Federal Fluminense
E. Armengaud, Universidad Nacional Autónoma de México
F. Arneodo, Michigan Technological University
F. Arqueros, Consejo Nacional de Investigaciones Científicas y Técnicas
T. Asch, Instituto de Astronomía y Física del Espacio
H. Asorey, Consejo Nacional de Investigaciones Científicas y Técnicas
B. S. Atulugama, Universidade Federal da Bahia
J. Aublin, Universidad Michoacana de San Nicolás de Hidalgo
M. Ave, Charles University
G. Avila, Karlsruhe Institute of Technology, Campus North
J. Bacelar, University of Colorado Boulder
T. Bäcker, Universidad de Alcala
D. Badagnani, Rheinisch-Westfälische Technische Hochschule Aachen
A. F. Barbosa, Università degli Studi dell'Aquila
H. M.J. Barbosa, Università degli Studi di Napoli Federico II
M. Barkhausen, Netherlands Foundation for Research in Astronomy
D. Barnhill, Universidade Federal Fluminense
S. L.C. Barroso, Università degli Studi dell'Aquila
P. Bauleo, Universidad Mayor de San Andres Bolivia
J. Beatty, Universidade Estadual do Sudoeste da Bahia

Document Type

Article

Publication Date

1-1-2007

Abstract

An upper limit of 16% (at 95% c.l.) is derived for the photon fraction in cosmic rays with energies greater than 1019 eV, based on observations of the depth of shower maximum performed with the hybrid detector of the Pierre Auger Observatory. This is the first such limit on photons obtained by observing the fluorescence light profile of air showers. This upper limit confirms and improves on previous results from the Haverah Park and AGASA surface arrays. Additional data recorded with the Auger surface detectors for a subset of the event sample support the conclusion that a photon origin of the observed events is not favored. © 2006 Elsevier B.V. All rights reserved.

Publication Title

Astroparticle Physics

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