Depth of maximum of air-shower profiles at the Pierre Auger Observatory. I. Measurements at energies above 10(17.8) eV
The successful installation, commissioning, and operation of the Pierre Auger Observatory would not have been possible without the strong commitment and effort from the technical and administrative staff in Malargue. We are very grateful to the following agencies and organizations for financial support: Comision Nacional de Energia Atomica, Fundacion Antorchas, Gobierno De La Provincia de Mendoza, Municipalidad de Malargue, NDM Holdings and Valle Las Lenas, in gratitude for their continuing cooperation over land access, Argentina; the Australian Research Council; Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq), Financiadora de Estudos e Projetos (FINEP), Fundacao de Amparo a Pesquisa do Estado de Rio de Janeiro (FAPERJ), Sao Paulo Research Foundation (FAPESP) Grants No. 2010/07359-6, No. 1999/05404-3, Ministerio de Ciencia e Tecnologia (MCT), Brazil; MSMT-CR LG13007, 7AMB14AR005, CZ.1.05/2.1.00/03.0058 and the Czech Science Foundation Grant No. 14-17501S, Czech Republic; Centre de Calcul IN2P3/CNRS, Centre National de la Recherche Scientifique (CNRS), Conseil Regional Ile-de-France, Departement Physique Nucleaire et Corpusculaire (PNC-IN2P3/CNRS), Departement Sciences de l'Univers (SDU-INSU/CNRS), Institut Lagrange de Paris, ILP LABEX ANR-10-LABX-63, within the Investissements d'Avenir Programme ANR-11-IDEX-0004-02, France; Bundesministerium fur Bildung und Forschung (BMBF), Deutsche Forschungsgemeinschaft (DFG), Finanzministerium Baden-Wurttemberg, Helmholtz-Gemeinschaft Deutscher Forschungszentren (HGF), Ministerium fur Wissenschaft und Forschung, Nordrhein Westfalen, Ministerium fur Wissenschaft, Forschung und Kunst, Baden-Wurttemberg, Germany; Istituto Nazionale di Fisica Nucleare (INFN), Ministero dell'Istruzione, dell'Universita e della Ricerca (MIUR), Gran Sasso Center for Astroparticle Physics (CFA), CETEMPS Center of Excellence, Italy; Consejo Nacional de Ciencia y Tecnologia (CONACYT), Mexico; Ministerie van Onderwijs, Cultuur en Wetenschap, Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO), Stichting voor Fundamenteel Onderzoek der Materie (FOM), Netherlands; National Centre for Research and Development, Grants No. ERA-NET-ASPERA/01/11 and No. ERA-NET-ASPERA/02/11, National Science Centre, Grants No. 2013/08/M/ST9/00322, No. 2013/08/M/ST9/00728 and No. HARMONIA 5 - 2013/10/M/ST9/00062, Poland; Portuguese national funds and FEDER funds within COMPETE - Programa Operacional Factores de Competitividade through Fundacao para a Ciencia e a Tecnologia, Portugal; Romanian Authority for Scientific Research ANCS, CNDI-UEFISCDI partnership projects nr. 20/2012 and nr. 194/2012, project nr. 1/ASPERA2/2012 ERA-NET, PN-II-RU-PD-2011-3-0145-17, and PN-II-RU-PD-2011-3-0062, the Minister of National Education, Programme for research - Space Technology and Advanced Research - STAR, project no. 83/2013, Romania; Slovenian Research Agency, Slovenia; Comunidad de Madrid, FEDER funds, Ministerio de Educacion y Ciencia, Xunta de Galicia, European Community 7th Framework Program, Grant No. FP7-PEOPLE-2012-IEF-328826, Spain; Science and Technology Facilities Council, U.K.; Department of Energy, Contracts No. DE-AC02-07CH11359, No. DE-FR02-04ER41300, No. DE-FG02-99ER41107 and No. DE-SC0011689, National Science Foundation, Grant No. 0450696, The Grainger Foundation, USA; NAFOSTED, Vietnam; Marie Curie-IRSES/EPLANET, European Particle Physics Latin American Network, European Union 7th Framework Program, Grant No. PIRSES-2009-GA-246806; and UNESCO. ; We report a study of the distributions of the depth of maximum, Xmax, of extensive air-shower profiles with energies above 1017.8 eV as observed with the fluorescence telescopes of the Pierre Auger Observatory. The analysis method for selecting a data sample with minimal sampling bias is described in detail as well as the experimental cross-checks and systematic uncertainties. Furthermore, we discuss the detector acceptance and the resolution of the Xmax measurement and provide parametrizations thereof as a function of energy. The energy dependence of the mean and standard deviation of the Xmax distributions are compared to air-shower simulations for different nuclear primaries and interpreted in terms of the mean and variance of the logarithmic mass distribution at the top of the atmosphere. ; Comision Nacional de Energia Atomica ; Fundacion Antorchas ; Gobierno De La Provincia de Mendoza ; Municipalidad de Malargue ; NDM Holdings ; Valle Las Lenas ; Australian Research Council ; National Council for Scientific and Technological Development (CNPq) ; Ciencia Tecnologia e Inovacao (FINEP) ; Carlos Chagas Filho Foundation for Research Support of the State of Rio de Janeiro (FAPERJ) ; Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP) 2010/07359-6 1999/05404-3 ; Ministerio de Ciencia e Tecnologia (MCT), Brazil ; Grant Agency of the Czech Republic Czech Republic Government 14-17501S ; Centre National de la Recherche Scientifique (CNRS) ; Region Ile-de-France ; Departement Sciences de l'Univers (SDU-INSU/CNRS) ; Institut Lagrange de Paris ; French National Research Agency (ANR) ANR-10-LABX-63 ANR-11-IDEX-0004-02 ; Federal Ministry of Education & Research (BMBF) ; German Research Foundation (DFG) ; Finanzministerium Baden-Wurttemberg ; Helmholtz Association ; Ministerium fur Wissenschaft und Forschung ; Nordrhein Westfalen ; Ministerium fur Wissenschaft ; Forschung und Kunst ; Baden-Wurttemberg, Germany ; Istituto Nazionale di Fisica Nucleare (INFN) ; Ministry of Education, Universities and Research (MIUR) ; Gran Sasso Center for Astroparticle Physics (CFA) ; CETEMPS Center of Excellence, Italy ; Consejo Nacional de Ciencia y Tecnologia (CONACyT) ; Ministerie van Onderwijs, Cultuur en Wetenschap ; Netherlands Organization for Scientific Research (NWO) ; FOM (The Netherlands) Netherlands Government ; National Centre for Research and Development ERA-NET-ASPERA/01/11 ERA-NET-ASPERA/02/11 ; National Science Centre, Poland 2013/08/M/ST9/00322 2013/08/M/ST9/00728 HARMONIA 5 - 2013/10/M/ST9/00062 ; Portuguese national funds within COMPETE - Programa Operacional Factores de Competitividade through Fundacao para a Ciencia e a Tecnologia, Portugal ; FEDER funds within COMPETE - Programa Operacional Factores de Competitividade through Fundacao para a Ciencia e a Tecnologia, Portugal ; Romanian Authority for Scientific Research ANCS ; CNDI-UEFISCDI 20/2012 194/2012 1/ASPERA2/2012 ERA-NET PN-II-RU-PD-2011-3-0145-17 PN-II-RU-PD-2011-3-0062 ; Minister of National Education, Programme for research - Space Technology and Advanced Research - STAR, Romania 83/2013 ; Slovenian Research Agency - Slovenia ; Comunidad de Madrid Instituto de Salud Carlos III ; European Union (EU) ; Spanish Government ; Xunta de Galicia ; European Community 7th Framework Program, Spain FP7-PEOPLE-2012-IEF-328826 ; Science & Technology Facilities Council (STFC) ; United States Department of Energy (DOE) DE-AC02-07CH11359 DE-FR02-04ER41300 DE-FG02-99ER41107 DE-SC0011689 ; National Science Foundation (NSF) 0450696 ; Grainger Foundation, USA ; National Foundation for Science & Technology Development (NAFOSTED) ; European Union (EU) PIRSES-2009-GA-246806 ; UNESCO ; MSMT-CR LG13007 ; 7AMB14AR005 ; CZ.1.05/2.1.00/03.0058