An upper limit to the photon fraction in cosmic rays above 1019eV from the Pierre Auger Observatory

J. Abraham,M. Aglietta,C. Aguirre,D. Allard,I. Allekotte,P. Allison,C. Alvarez,J. Alvarez-Muñiz,M. Ambrosio,L. Anchordoqui,J.C. Anjos,C. Aramo,K. Arisaka,E. Armengaud,F. Arneodo,F. Arqueros,T. Asch,H. Asorey,B.S. Atulugama,J. Aublin,M. Ave,G. Avila,J. Bacelar,T. Bäcker,D. Badagnani,A.F. Barbosa,H.M.J. Barbosa,M. Barkhausen,D. Barnhill,S.L.C. Barroso,P. Bauleo,J. Beatty,T. Beau,B.R. Becker,K.H. Becker,J.A. Bellido,S. BenZvi,C. Berat,T. Bergmann,P. Bernardini,X. Bertou,P.L. Biermann,P. Billoir,O. Blanch-Bigas,F. Blanco,P. Blasi,C. Bleve,H. Blümer,P. Boghrat,M. Boháčová,C. Bonifazi,R. Bonino,M. Boratav,J. Brack,J.M. Brunet,P. Buchholz,N.G. Busca,K.S. Caballero-Mora,B. Cai,D.V. Camin,J.N. Capdevielle,R. Caruso,A. Castellina,G. Cataldi,L. Cazón,R. Cester,J. Chauvin,A. Chiavassa,J.A. Chinellato,A. Chou,J. Chye,D. Claes,P.D.J. Clark,R.W. Clay,S.B. Clay,B. Connolly,A. Cordier,U. Cotti,S. Coutu,C.E. Covault,J. Cronin,S. Dagoret-Campagne,T. Dang Quang,P. Darriulat,K. Daumiller,B.R. Dawson,R.M. de Almeida,L.A. de Carvalho,C. De Donato,S.J. de Jong,W.J.M. de Mello,J.R.T. de Mello Neto,I. De Mitri,M.A.L. de Oliveira,V. de Souza,L. del Peral,O. Deligny,A. Della Selva,C. Delle Fratte,H. Dembinski,C. Di Giulio,J.C. Diaz,C. Dobrigkeit,J.C. D’Olivo,D. Dornic,A. Dorofeev,M.T. Dova,D. D’Urso,M.A. DuVernois,R. Engel,L. Epele,M. Erdmann,C.O. Escobar,A. Etchegoyen,A. Ewers,P. Facal San Luis,H. Falcke,A.C. Fauth,D. Fazio,N. Fazzini,A. Fernández,F. Ferrer,S. Ferry,B. Fick,A. Filevich,A. Filipčič,I. Fleck,E. Fokitis,R. Fonte,D. Fuhrmann,W. Fulgione,B. García,D. Garcia-Pinto,L. Garrard,X. Garrido,H. Geenen,G. Gelmini,H. Gemmeke,A. Geranios,P.L. Ghia,M. Giller,J. Gitto,H. Glass,F. Gobbi,M.S. Gold,F. Gomez Albarracin,M. Gómez Berisso,R. Gómez Herrero,M. Gonçalves do Amaral,J.P. Gongora,D. Gonzalez,J.G. Gonzalez,M. González,D. Góra,A. Gorgi,P. Gouffon,V. Grassi,A. Grillo,C. Grunfeld,C. Grupen,F. Guarino,G.P. Guedes,J. Gutiérrez,J.D. Hague,J.C. Hamilton,M.N. Harakeh,D. Harari,S. Harmsma,S. Hartmann,J.L. Harton,M.D. Healy,T. Hebbeker,D. Heck,C. Hojvat,P. Homola,J. Hörandel,A. Horneffer,M. Horvat,M. Hrabovský,M. Iarlori,A. Insolia,M. Kaducak,O. Kalashev,K.H. Kampert,B. Keilhauer,E. Kemp,H.O. Klages,M. Kleifges,J. Kleinfeller,R. Knapik,J. Knapp,D.-H. Koang,Y. Kolotaev,A. Kopmann,O. Krömer,S. Kuhlman,J. Kuijpers,N. Kunka,A. Kusenko,C. Lachaud,B.L. Lago,D. Lebrun,P. LeBrun,J. Lee,A. Letessier-Selvon,M. Leuthold,I. Lhenry-Yvon,G. Longo,R. López,A. Lopez Agüera,A. Lucero,S. Maldera,M. Malek,S. Maltezos,G. Mancarella,M.E. Manceñido,D. Mandat,P. Mantsch,A.G. Mariazzi,I.C. Maris,D. Martello,N. Martinez,J. Martínez,O. Martínez,H.J. Mathes,J. Matthews,J.A.J. Matthews,G. Matthiae,G. Maurin,D. Maurizio,P.O. Mazur,T. McCauley,M. McEwen,R.R. McNeil,G. Medina,M.C. Medina,G. Medina Tanco,A. Meli,D. Melo,E. Menichetti,A. Menshikov,Chr. Meurer,R. Meyhandan,M.I. Micheletti,G. Miele,W. Miller,S. Mollerach,M. Monasor,D. Monnier Ragaigne,F. Montanet,B. Morales,C. Morello,E. Moreno,C. Morris,M. Mostafá,M.A. Muller,R. Mussa,G. Navarra,L. Nellen,C. Newman-Holmes,D. Newton,T. Nguyen Thi,R. Nichol,N. Nierstenhöfer,D. Nitz,H. Nogima,D. Nosek,L. Nožka,J. Oehlschläger,T. Ohnuki,A. Olinto,L.F.A. Oliveira,V.M. Olmos-Gilbaja,M. Ortiz,S. Ostapchenko,L. Otero,M. Palatka,J. Pallotta,G. Parente,E. Parizot,S. Parlati,M. Patel,T. Paul,K. Payet,M. Pech,J. Pe¸kala,R. Pelayo,I.M. Pepe,L. Perrone,S. Petrera,P. Petrinca,Y. Petrov,D. Pham Ngoc,T.N. Pham Thi,R. Piegaia,T. Pierog,O. Pisanti,T.A. Porter,J. Pouryamout,L. Prado,P. Privitera,M. Prouza,E.J. Quel,J. Rautenberg,H.C. Reis,S. Reucroft,B. Revenu,J. Řídký,A. Risi,M. Risse,C. Rivière,V. Rizi,S. Robbins,M. Roberts,C. Robledo,G. Rodriguez,D. Rodríguez Frías,J. Rodriguez Martino,J. Rodriguez Rojo,G. Ros,J. Rosado,M. Roth,C. Roucelle,B. Rouillé-d’Orfeuil,E. Roulet,A.C. Rovero,F. Salamida,H. Salazar,G. Salina,F. Sánchez,M. Santander,E.M. Santos,S. Sarkar,R. Sato,V. Scherini,T. Schmidt,O. Scholten,P. Schovánek,F. Schüssler,S.J. Sciutto,M. Scuderi,D. Semikoz,G. Sequeiros,R.C. Shellard,B.B. Siffert,G. Sigl,P. Skelton,W. Slater,N. Smetniansky De Grande,A. Smiałkowski,R. Šmída,B.E. Smith,G.R. Snow,P. Sokolsky,P. Sommers,J. Sorokin,H. Spinka,E. Strazzeri,A. Stutz,F. Suarez,T. Suomijärvi,A.D. Supanitsky,J. Swain,Z. Szadkowski,A. Tamashiro,A. Tamburro,O. Tascau,R. Ticona,C. Timmermans,W. Tkaczyk,C.J. Todero Peixoto,A. Tonachini,D. Torresi,P. Travnicek,A. Tripathi,G. Tristram,D. Tscherniakhovski,M. Tueros,V. Tunnicliffe,R. Ulrich,M. Unger,M. Urban,J.F. Valdés Galicia,I. Valiño,L. Valore,A.M. van den Berg,V. van Elewyck,R.A. Vazquez,D. Veberič,A. Veiga,A. Velarde,T. Venters,V. Verzi,M. Videla,L. Villaseñor,T. Vo Van,S. Vorobiov,L. Voyvodic,H. Wahlberg,O. Wainberg,T. Waldenmaier,P. Walker,D. Warner,A.A. Watson,S. Westerhoff,C. Wiebusch,G. Wieczorek,L. Wiencke,B. Wilczyńska,H. Wilczyński,C. Wileman,M.G. Winnick,J. Xu,T. Yamamoto,P. Younk,E. Zas,D. Zavrtanik,M. Zavrtanik,A. Zech,A. Zepeda,M. Zha,M. Ziolkowski

Astroparticle Physics（2007）

Cited 99|Views68

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Abstract

An upper limit of 16% (at 95% c.l.) is derived for the photon fraction in cosmic rays with energies greater than 1019eV, 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.

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Key words

Cosmic rays,Ultra-high energy photons,Extensive air showers,Pierre Auger Observatory

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