Depth of maximum of air-shower profiles at the Pierre Auger Observatory. II. Composition implications
A. AabUniversität Siegen, Siegen, GermanyP. AbreuLaboratório de Instrumentação e Física Experimental de Partículas (LIP) and Instituto Superior Técnico (IST), Universidade de Lisboa (UL), PortugalM. AgliettaOsservatorio Astrofisico di Torino (INAF), Università di Torino and Sezione INFN, Torino, ItalyE. J. AhnFermilab, Batavia, Illinois, USAI. Al SamaraiInstitut de Physique Nucléaire d’Orsay (IPNO), Université Paris 11, CNRS-IN2P3, Orsay, FranceI. F. M. AlbuquerqueUniversidade de São Paulo, Instituto de Física, São Paulo, São Paulo, BrazilI. AllekotteBalseiro InstituteJ. AllenNew York University, New York, New York, USAP. AllisonOhio State University, Columbus, Ohio, USAA. AlmelaInstituto de Tecnologías en Detección y Astropartículas (CNEA, CONICET, UNSAM), Buenos Aires, ArgentinaJ. Alvarez CastilloUniversidad Nacional Autonoma de Mexico, Mexico, Distrito Federal, MexicoJaime Álvarez-MuñizUniversidad de Santiago de Compostela, SpainRafael Alves BatistaUniversität Hamburg, Hamburg, GermanyM. AmbrosioUniversità di Napoli “Federico II” and Sezione INFN, Napoli, ItalyA. AminaeiIMAPP, Radboud University, Nijmegen, NetherlandsLuis A. AnchordoquiDepartment of Physics and Astronomy, Lehman College, City University of New York, New York, USAS. AndringaLaboratório de Instrumentação e Física Experimental de Partículas (LIP) and Instituto Superior Técnico (IST), Universidade de Lisboa (UL), PortugalC. AramoUniversità di Napoli “Federico II” and Sezione INFN, Napoli, ItalyV. ArandaUniversidad Complutense de Madrid, Madrid, SpainF. ArquerosUniversidad Complutense de Madrid, Madrid, SpainH. AsoreyCentro Atómico Bariloche and Instituto Balseiro (CNEA-UNCuyo-CONICET), San Carlos de Bariloche, ArgentinaP. AssisLaboratório de Instrumentação e Física Experimental de Partículas (LIP) and Instituto Superior Técnico (IST), Universidade de Lisboa (UL), PortugalJ. AublinLaboratoire de Physique Nucléaire et de Hautes Energies (LPNHE), Universités Paris 6 et Paris 7, CNRS-IN2P3 Paris, FranceM. AveUniversidad de Santiago de Compostela, SpainM. AvenierLaboratoire de Physique Subatomique et de Cosmologie (LPSC), Université Grenoble-Alpes, CNRS/IN2P3, FranceG. ÁvilaObservatorio Pierre Auger and Comisión Nacional de Energía Atómica, Malargüe, ArgentinaN. AwalNew York University, New York, New York, USAAlina Mihaela BadescuUniversity Politehnica of Bucharest, RomaniaK. B. BarberUniversity of Adelaide, Adelaide, South Australia, AustraliaJ. BäumlKarlsruhe Institute of Technology—Campus South—Institut für Experimentelle Kernphysik (IEKP), Karlsruhe, GermanyC. BausKarlsruhe Institute of Technology—Campus South—Institut für Experimentelle Kernphysik (IEKP), Karlsruhe, GermanyJ. J. BeattyOhio State University, Columbus, Ohio, USAKlaus BeckerBergische Universität Wuppertal, Wuppertal, GermanyJ. A. BellidoUniversity of Adelaide, Adelaide, South Australia, AustraliaC. BératLaboratoire de Physique Subatomique et de Cosmologie (LPSC), Université Grenoble-Alpes, CNRS/IN2P3, FranceMario BertaniaOsservatorio Astrofisico di Torino (INAF), Università di Torino and Sezione INFN, Torino, ItalyX. BertouCentro Atómico Bariloche and Instituto Balseiro (CNEA-UNCuyo-CONICET), San Carlos de Bariloche, ArgentinaPeter L. BiermannMax-Planck-Institut für Radioastronomie, Bonn, GermanyP. BilloirLaboratoire de Physique Nucléaire et de Hautes Energies (LPNHE), Universités Paris 6 et Paris 7, CNRS-IN2P3 Paris, FranceS. G. BlaessUniversity of Adelaide, Adelaide, South Australia, AustraliaF. BlancoLaboratoire de Physique Nucléaire et de Hautes Energies (LPNHE), Universités Paris 6 et Paris 7, CNRS-IN2P3 Paris, FranceC. BleveDipartimento di Matematica e Fisica “E. De Giorgi” dell’Università del Salento and Sezione INFN, Lecce, ItalyH. BlümerKarlsruhe Institute of Technology—Campus North—Institut für Kernphysik, Karlsruhe, GermanyM. BoháčováInstitute of Physics of the Academy of Sciences of the Czech Republic, Prague, Czech RepublicDenise BoncioliINFN, Laboratori Nazionali del Gran Sasso, Assergi (L’Aquila), ItalyC. BonifaziUniversidade Federal do Rio de Janeiro, Instituto de Física, Rio de Janeiro, Rio de Janeiro, BrazilR. BoninoOsservatorio Astrofisico di Torino (INAF), Università di Torino and Sezione INFN, Torino, ItalyNataliia BorodaiInstitute of Nuclear Physics PAN, Krakow, PolandJ. BrackColorado State University, Fort Collins, Colorado, USAI.M. Brâncuş’Horia Hulubei’ National Institute for Physics and Nuclear Engineering, Bucharest-Magurele, RomaniaA. BridgemanKarlsruhe Institute of Technology—Campus North—Institut für Kernphysik, Karlsruhe, GermanyP. BrogueiraLaboratório de Instrumentação e Física Experimental de Partículas (LIP) and Instituto Superior Técnico (IST), Universidade de Lisboa (UL), PortugalW. C. BrownColorado State University, Pueblo, Colorado, USAP. BuchholzUniversität Siegen, Siegen, GermanyA. BuenoUniversidad de Granada and C.A.F.P.E., Granada, SpainS. BuitinkIMAPP, Radboud University, Nijmegen, NetherlandsMario BuscemiUniversità di Napoli “Federico II” and Sezione INFN, Napoli, ItalyK. S. Caballero‐MoraCentro de Investigación y de Estudios Avanzados del IPN (CINVESTAV), México, Distrito Federal, MexicoB. CaccianigaUniversità di Milano and Sezione INFN, Milan, ItalyLorenzo CaccianigaLaboratoire de Physique Nucléaire et de Hautes Energies (LPNHE), Universités Paris 6 et Paris 7, CNRS-IN2P3 Paris, FranceM. CandussoUniversità di Roma II “Tor Vergata” and Sezione INFN, Roma, ItalyL. CarameteMax-Planck-Institut für Radioastronomie, Bonn, GermanyR. CarusoUniversità di Catania and Sezione INFN, Catania, ItalyA. CastellinaOsservatorio Astrofisico di Torino (INAF), Università di Torino and Sezione INFN, Torino, ItalyG. CataldiDipartimento di Matematica e Fisica “E. De Giorgi” dell’Università del Salento and Sezione INFN, Lecce, ItalyLorenzo CazonLaboratório de Instrumentação e Física Experimental de Partículas (LIP) and Instituto Superior Técnico (IST), Universidade de Lisboa (UL), PortugalR. CesterUniversità di Torino and Sezione INFN, Torino, ItalyA. G. ChavezUniversidad Michoacana de San Nicolas de Hidalgo, Morelia, Michoacan, MexicoA. ChiavassaOsservatorio Astrofisico di Torino (INAF), Università di Torino and Sezione INFN, Torino, ItalyC. DobrigkeitUniversidade Estadual de Campinas, IFGW, Campinas, São Paulo, BrazilJ. ChudobaInstitute of Physics of the Academy of Sciences of the Czech Republic, Prague, Czech RepublicM. CilmoUniversità di Napoli “Federico II” and Sezione INFN, Napoli, ItalyR. W. ClayUniversity of Adelaide, Adelaide, South Australia, AustraliaG. CoccioloDipartimento di Matematica e Fisica “E. De Giorgi” dell’Università del Salento and Sezione INFN, Lecce, ItalyRoberta ColalilloUniversità di Napoli “Federico II” and Sezione INFN, Napoli, ItalyAlan ColemanPennsylvania State University, University Park, USAL. CollicaUniversità di Milano and Sezione INFN, Milan, ItalyM. R. ColucciaDipartimento di Matematica e Fisica “E. De Giorgi” dell’Università del Salento and Sezione INFN, Lecce, ItalyR. ConceiçãoLaboratório de Instrumentação e Física Experimental de Partículas (LIP) and Instituto Superior Técnico (IST), Universidade de Lisboa (UL), PortugalF. ContrerasObservatorio Pierre Auger, Malargüe, ArgentinaM. J. CooperUniversity of Adelaide, Adelaide, South Australia, AustraliaA. CordierLaboratoire de l’Accélérateur Linéaire (LAL), Université Paris 11, CNRS-IN2P3 Orsay, FranceS. CoutuPennsylvania State University, University Park, USAC. E. CovaultCase Western Reserve University, Cleveland, Ohio, USAJ. CroninUniversity of Chicago, Enrico Fermi Institute, Chicago, Illinois, USAA. CurutiuMax-Planck-Institut für Radioastronomie, Bonn, GermanyR. DallierSUBATECH, École des Mines de Nantes, CNRS-IN2P3, Université de Nantes, Nantes, FranceB. DanielUniversidade Estadual de Campinas, IFGW, Campinas, São Paulo, BrazilS. DassoDepartamento de Física, FCEyN, Universidad de Buenos Aires y CONICET, ArgentinaK. DaumillerKarlsruhe Institute of Technology—Campus North—Institut für Kernphysik, Karlsruhe, GermanyB. R. DawsonUniversity of Adelaide, Adelaide, South Australia, AustraliaR. M. de AlmeidaUniversidade Federal Fluminense, EEIMVR, Volta Redonda, Rio de Janeiro, BrazilManlio De DomenicoUniversità di Catania and Sezione INFN, Catania, ItalyS. J. de JongIMAPP, Radboud University, Nijmegen, NetherlandsJ. R. T. de Mello NetoUniversidade Federal do Rio de Janeiro, Instituto de Física, Rio de Janeiro, Rio de Janeiro, BrazilI. De MitriDipartimento di Matematica e Fisica “E. De Giorgi” dell’Università del Salento and Sezione INFN, Lecce, ItalyJaime de OliveiraUniversidade Federal Fluminense, EEIMVR, Volta Redonda, Rio de Janeiro, BrazilV. de SouzaUniversidade de São Paulo, Instituto de Física de São Carlos, São Carlos, São Paulo, BrazilL. del PeralUniversidad de Alcalá, Alcalá de Henares, SpainO. DelignyInstitut de Physique Nucléaire d’Orsay (IPNO), Université Paris 11, CNRS-IN2P3, Orsay, France
2014en
ABI
Abstract
Using the data taken at the Pierre Auger Observatory between December 2004 and December 2012, we have examined the implications of the distributions of depths of atmospheric shower maximum (${X}_{\mathrm{max}}$), using a hybrid technique, for composition and hadronic interaction models. We do this by fitting the distributions with predictions from a variety of hadronic interaction models for variations in the composition of the primary cosmic rays and examining the quality of the fit. Regardless of what interaction model is assumed, we find that our data are not well described by a mix of protons and iron nuclei over most of the energy range. Acceptable fits can be obtained when intermediate masses are included, and when this is done consistent results for the proton and iron-nuclei contributions can be found using the available models. We observe a strong energy dependence of the resulting proton fractions, and find no support from any of the models for a significant contribution from iron nuclei. However, we also observe a significant disagreement between the models with respect to the relative contributions of the intermediate components.
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Cited by 40 references