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arXiv · 0903.1127

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

The Pierre Auger Collaboration·J. Abraham·P. Abreu·M. Aglietta·C. Aguirre·E. J. Ahn·D. Allard·I. Allekotte·J. Allen·P. Allison·J. Alvarez-Muñiz·M. Ambrosio·L. Anchordoqui·S. Andringa·A. Anzalone·C. Aramo·S. Argiró·K. Arisaka·F. Arneodo·F. Arqueros·T. Asch·H. Asorey·P. Assis·J. Aublin·M. Ave·G. Avila·T. Bäcker·D. Badagnani·K. B. Barber·A. F. Barbosa·S. L. C. Barroso·B. Baughman·P. Bauleo·J. J. Beatty·T. Beau·B. R. Becker·K. H. Becker·A. Bellétoile·J. A. Bellido·S. BenZvi·C. Berat·P. Bernardini·X. Bertou·P. L. Biermann·P. Billoir·O. Blanch-Bigas·F. Blanco·C. Bleve·H. Blümer·M. Boháčová·C. Bonifazi·R. Bonino·J. Brack·P. Brogueira·W. C. Brown·R. Bruijn·P. Buchholz·A. Bueno·R. E. Burton·N. G. Busca·K. S. Caballero-Mora·L. Caramete·R. Caruso·W. Carvalho·A. Castellina·O. Catalano·L. Cazon·R. Cester·J. Chauvin·A. Chiavassa·J. A. Chinellato·A. Chou·J. Chudoba·J. Chye·R. W. Clay·E. Colombo·R. Conceição·B. Connolly·F. Contreras·J. Coppens·A. Cordier·U. Cotti·S. Coutu·C. E. Covault·A. Creusot·A. Criss·J. Cronin·A. Curutiu·S. Dagoret-Campagne·K. Daumiller·B. R. Dawson·R. M. de Almeida·M. De Domenico·C. De Donato·S. J. de Jong·G. De La Vega·W. J. M. de Mello Junior·J. R. T. de Mello Neto·I. De Mitri·V. de Souza
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Abstract

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.

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The Pierre Auger Collaboration, J. Abraham, P. Abreu, M. Aglietta, C. Aguirre, E. J. Ahn, D. Allard, I. Allekotte, J. Allen, P. Allison, J. Alvarez-Muñiz, M. Ambrosio, L. Anchordoqui, S. Andringa, A. Anzalone, C. Aramo, S. Argiró, K. Arisaka, F. Arneodo, F. Arqueros, T. Asch, H. Asorey, P. Assis, J. Aublin, M. Ave, G. Avila, T. Bäcker, D. Badagnani, K. B. Barber, A. F. Barbosa, S. L. C. Barroso, B. Baughman, P. Bauleo, J. J. Beatty, T. Beau, B. R. Becker, K. H. Becker, A. Bellétoile, J. A. Bellido, S. BenZvi, C. Berat, P. Bernardini, X. Bertou, P. L. Biermann, P. Billoir, O. Blanch-Bigas, F. Blanco, C. Bleve, H. Blümer, M. Boháčová, C. Bonifazi, R. Bonino, J. Brack, P. Brogueira, W. C. Brown, R. Bruijn, P. Buchholz, A. Bueno, R. E. Burton, N. G. Busca, K. S. Caballero-Mora, L. Caramete, R. Caruso, W. Carvalho, A. Castellina, O. Catalano, L. Cazon, R. Cester, J. Chauvin, A. Chiavassa, J. A. Chinellato, A. Chou, J. Chudoba, J. Chye, R. W. Clay, E. Colombo, R. Conceição, B. Connolly, F. Contreras, J. Coppens, A. Cordier, U. Cotti, S. Coutu, C. E. Covault, A. Creusot, A. Criss, J. Cronin, A. Curutiu, S. Dagoret-Campagne, K. Daumiller, B. R. Dawson, R. M. de Almeida, M. De Domenico, C. De Donato, S. J. de Jong, G. De La Vega, W. J. M. de Mello Junior, J. R. T. de Mello Neto, I. De Mitri, V. de Souza. 2009-03-05. Upper limit on the cosmic-ray photon fraction at EeV energies from the Pierre Auger Observatory. https://doi.org/10.1016/j.astropartphys.2009.04.003

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