Upper limit on the cosmic-ray photon fraction at EeV energies from the Pierre Auger Observatory
Creators: name: The Pierre Auger Collaboration
name: Abraham, J.
name: Abreu, P.
name: Aglietta, M.
name: Aguirre, C.
name: Ahn, E. J.
name: Allard, D.
name: Allekotte, I.
name: Allen, J.
name: Allison, P.
name: Alvarez-Muñiz, J.
name: Ambrosio, M.
name: Anchordoqui, L.
name: Andringa, S.
name: Anzalone, A.
name: Aramo, C.
name: Argiró, S.
name: Arisaka, K.
name: Arneodo, F.
name: Arqueros, F.
name: Asch, T.
name: Asorey, H.
name: Assis, P.
name: Aublin, J.
name: Ave, M.
name: Avila, G.
name: Bäcker, T.
name: Badagnani, D.
name: Barber, K. B.
name: Barbosa, A. F.
name: Barroso, S. L. C.
name: Baughman, B.
name: Bauleo, P.
name: Beatty, J. J.
name: Beau, T.
name: Becker, B. R.
name: Becker, K. H.
name: Bellétoile, A.
name: Bellido, J. A.
name: BenZvi, S.
name: Berat, C.
name: Bernardini, P.
name: Bertou, X.
name: Biermann, P. L.
name: Billoir, P.
name: Blanch-Bigas, O.
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name: Boháčová, M.
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name: Bonino, R.
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name: Brogueira, P.
name: Brown, W. C.
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name: Caballero-Mora, K. S.
name: Caramete, L.
name: Caruso, R.
name: Carvalho, W.
name: Castellina, A.
name: Catalano, O.
name: Cazon, L.
name: Cester, R.
name: Chauvin, J.
name: Chiavassa, A.
name: Chinellato, J. A.
name: Chou, A.
name: Chudoba, J.
name: Chye, J.
name: Clay, R. W.
name: Colombo, E.
name: Conceição, R.
name: Connolly, B.
name: Contreras, F.
name: Coppens, J.
name: Cordier, A.
name: Cotti, U.
name: Coutu, S.
name: Covault, C. E.
name: Creusot, A.
name: Criss, A.
name: Cronin, J.
name: Curutiu, A.
name: Dagoret-Campagne, S.
name: Daumiller, K.
name: Dawson, B. R.
name: de Almeida, R. M.
name: De Domenico, M.
name: De Donato, C.
name: de Jong, S. J.
name: De La Vega, G.
name: Junior, W. J. M. de Mello
name: Neto, J. R. T. de Mello
name: De Mitri, I.
name: de Souza, V.
name: Decerprit, G.
name: del Peral, L.
name: Deligny, O.
name: Della Selva, A.
name: Fratte, C. Delle
name: Dembinski, H.
name: Di Giulio, C.
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name: Diep, P. N.
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name: D'Olivo, J. C.
name: Dong, P. N.
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name: Dorofeev, A.
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name: DuVernois, M. A.
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name: Italiano, A.
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name: López, R.
name: Agüera, A. Lopez
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Publisher: name: arXiv
Year: 2009
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: 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.
description: 20 pages, 7 figures, 2 tables. Minor changes. Accepted by Astroparticle Physics