Techniques for measuring aerosol attenuation using the Central Laser Facility at the Pierre Auger Observatory

The Pierre Auger Observatory in Malargue, Argentina, is designed to study the properties of ultra-high energy cosmic rays with energies above 10(18) eV. It is a hybrid facility that employs a Fluorescence Detector to perform nearly calorimetric measurements of Extensive Air Shower energies. To obtain reliable calorimetric information from the FD, the atmospheric conditions at the observatory need to be continuously monitored during data acquisition. In particular, light attenuation due to aerosols is an important atmospheric correction. The aerosol concentration is highly variable, so that the aerosol attenuation needs to be evaluated hourly. We use light from the Central Laser Facility, located near the center of the observatory site, having an optical signature comparable to that of the highest energy showers detected by the FD. This paper presents two procedures developed to retrieve the aerosol attenuation of fluorescence light from CLF laser shots. Cross checks between the two methods demonstrate that results from both analyses are compatible, and that the uncertainties are well understood. The measurements of the aerosol attenuation provided by the two procedures are currently used at the Pierre Auger Observatory to reconstruct air shower data.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), Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP), Ministerio de Ciencia e Tecnologia (MCT), Brazil; AVCR AV0Z10100502 and AV0Z10100522, GAAV KJB100100904, MSMT-CR LA08016, LC527, 1M06002, MEB111003, and MSM0021620859, 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), 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), 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; Ministry of Science and Higher Education, Grant Nos. N N202 200239 and N N202 207238, Poland; Fundacao para a Ciencia e a Tecnologia, Portugal; Ministry for Higher Education, Science, and Technology, Slovenian Research Agency, Slovenia; Comunidad de Madrid, Consejeria de Educacion de la Comunidad de Castilla La Mancha, FEDER funds, Ministerio de Ciencia e Innovacion and Consolider-Ingenio 2010 (CPAN), Xunta de Galicia, Spain; Science and Technology Facilities Council, United Kingdom; Department of Energy, Contract Nos. DE-AC02-07CH11359, DE-FR02-04ER41300, National Science Foundation, Grant Nos. 0450696, 0855680, The Grainger Foundation USA; NAFOSTED, Vietnam; ALFA-EC /HE-LEN, European Union 6th Framework Program, Grant No. MEIF-CT-2005-025057, European Union 7th Framework Program, Grant No. PIEF-GA-2008-220240, and UNESCO.Peer reviewe

A Search for Photons with Energies Above 2 x 10(17) eV Using Hybrid Data from the Low-Energy Extensions of the Pierre Auger Observatory

Ultra-high-energy photons with energies exceeding 1017 eV offer a wealth of connections to different aspects of cosmic-ray astrophysics as well as to gamma-ray and neutrino astronomy. The recent observations of photons with energies in the 1015 eV range further motivate searches for even higher-energy photons. In this paper, we present a search for photons with energies exceeding 2 × 1017 eV using about 5.5 yr of hybrid data from the low-energy extensions of the Pierre Auger Observatory. The upper limits on the integral photon flux derived here are the most stringent ones to date in the energy region between 1017 and 1018 eV.Argentina-Comision Nacional de Energia AtomicaANPCyTArgentina-Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET) Argentina-Gobierno de la Provincia de Mendoza Argentina-Municipalidad de Malargue Argentina-NDM HoldingsAustralian Research CouncilBelgium-Fonds de la Recherche Scientifique (FNRS)FWOConselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPQ) Fundacao de Apoio a Pesquisa do Distrito Federal (FAPDF) Brazil-Financiadora de Estudos e Projetos (FINEP) Fundacao Carlos Chagas Filho de Amparo a Pesquisa do Estado do Rio De Janeiro (FAPERJ) Brazil-Sao Paulo Research Foundation (FAPESP) 2019/10151-2 2010/07359-6 1999/05404-3 Brazil-Ministerio da Ciencia, Tecnologia, Inovacoes e Comunicacoes (MCTIC)France-Centre de Calcul IN2P3/CNRS Centre National de la Recherche Scientifique (CNRS) France-Conseil Regional Ile-deFrance France-Departement Physique Nucleaire et Corpusculaire (PNC-IN2P3/CNRS) France-Departement Sciences de l'Univers (SDU-INSU/CNRS) France-Institut Lagrange de Paris (ILP) LABEX ANR-10-LABX-63 ANR-11-IDEX-0004-02Federal Ministry of Education & Research (BMBF) German Research Foundation (DFG) Germany-Finanzministerium Baden-Wurttemberg Germany-Helmholtz Alliance for Astroparticle Physics (HAP) Germany-Helmholtz-Gemeinschaft Deutscher Forschungszentren (HGF) Germany-Ministerium fur Innovation, Wissenschaft und Forschung des Landes Nordrhein-Westfalen Germany-Ministerium fur Wissenschaft, Forschung und Kunst des Landes Baden-WurttembergItaly-Istituto Nazionale di Fisica Nucleare (INFN) Italy-Istituto Nazionale di Astrofisica (INAF) Italy-Ministero dell'Istruzione, dell'Universita e della Ricerca (MIUR) Italy-CETEMPS Center of Excellence Italy-Ministero degli Affari Esteri (MAE)Consejo Nacional de Ciencia y Tecnologia (CONACyT) 167733Mexico-Universidad Nacional Autonoma de Mexico (UNAM) Mexico-PAPIIT DGAPA-UNAMThe Netherlands-Ministry of Education, Culture and Science The Netherlands-Netherlands Organisation for Scientific Research (NWO) The Netherlands-Dutch national e-infrastructure The Netherlands-SURF CooperativePoland -Ministry of Education and Science DIR/WK/2018/11 Poland -National Science Centre 2016/22/M/ST9/00198 2016/23/B/ST9/01635 2020/39/B/ST9/01398Portuguese Foundation for Science and Technology Portugal-FEDER funds within Programa Operacional Factores de Competitividade through Fundacao para a Ciencia e a Tecnologia (COMPETE)Romania-Ministry of Research, Innovation and Digitization, CNCS/CCCDI-UEFISCDI, within PNCDI III PN19150201/16N/2019 PN1906010 TE128 PED289Slovenian Research Agency - Slovenia P1-0031 P1-0385 I0-0033 N1-0111Spanish Government FPA2017-85114-P PID-2019104676GB-C32Spain-Xunta de Galicia ED431C 2017/07 Spain-Junta de Andalucia Feder Funds SOMM17/6104/UGR P18-FR-4314 Spain-RENATA Red Nacional Tematica de Astroparticulas FPA2015-68783-REDT Spain-Maria de Maeztu Unit of Excellence MDM-2016-0692United States Department of Energy (DOE) DE-AC02-07CH11359 DE-FR02-04ER41300 DE-FG02-99ER41107 DE-SC0011689National Science Foundation (NSF) 0450696USA-Grainger Foundation USA-Marie Curie-IRSES/EPLANET USA-European Particle Physics Latin American Network USA-UNESCOArgentina-Valle Las Lenas MSMT CR LTT18004 LM2015038 LM2018102 CZ.02.1.01/0.0/0.0/16_013/0001402 CZ.02.1.01/0.0/0.0/18_046/0016010 CZ.02.1.01/0.0/0.0/17_049/000842

Testing effects of Lorentz invariance violation in the propagation of astroparticles with the Pierre Auger Observatory

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 Malargüe. We are very grateful to the following agencies and organizations for financial support: Argentina — Comisión Nacional de Energía Atómica; Agencia Nacional de Promoción Científica y Tecnológica (ANPCyT); Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET); Gobierno de la Provincia de Mendoza; Municipalidad de Malargüe; NDM Holdings and Valle Las Leñas; in gratitude for their continuing cooperation over land access; Australia — the Australian Research Council; Belgium — Fonds de la Recherche Scientifique (FNRS); Research Foundation Flanders (FWO); Brazil — Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq); Financiadora de Estudos e Projetos (FINEP); Fundação de Amparo à Pesquisa do Estado de Rio de Janeiro (FAPERJ); São Paulo Research Foundation (FAPESP) Grants No. 2019/10151-2, No. 2010/07359-6 and No. 1999/05404-3; Ministério da Ciência, Tecnologia, Inovações e Comunicações (MCTIC); Czech Republic — Grant No. MSMT CR LTT18004, LM2015038, LM2018102, CZ.02.1.01/0.0/0.0/16_013/0001402, CZ.02.1.01/0.0/0.0/18_046/0016010 and CZ.02.1.01/0.0/0.0/17_049/0008422; France — Centre de Calcul IN2P3/CNRS; Centre National de la Recherche Scientifique (CNRS); Conseil Régional Ile-de-France; Département Physique Nucléaire et Corpusculaire (PNC-IN2P3/CNRS); Département Sciences de l’Univers (SDU-INSU/CNRS); Institut Lagrange de Paris (ILP) Grant No. LABEX ANR-10-LABX-63 within the Investissements d’Avenir Programme Grant No. ANR-11-IDEX-0004-02; Germany — Bundesministerium für Bildung und Forschung (BMBF); Deutsche Forschungsgemeinschaft (DFG); Finanzministerium Baden-Württemberg; Helmholtz Alliance for Astroparticle Physics (HAP); Helmholtz-Gemeinschaft Deutscher Forschungszentren (HGF); Ministerium für Innovation, Wissenschaft und Forschung des Landes Nordrhein-Westfalen; Ministerium für Wissenschaft, Forschung und Kunst des Landes Baden-Württemberg; Italy — Istituto Nazionale di Fisica Nucleare (INFN); Istituto Nazionale di Astrofisica (INAF); Ministero dell’Istruzione, dell’Università e della Ricerca (MIUR); CETEMPS Center of Excellence; Ministero degli Affari Esteri (MAE); México — Consejo Nacional de Ciencia y Tecnología (CONACYT) No. 167733; Universidad Nacional Autónoma de México (UNAM); PAPIIT DGAPA-UNAM; The Netherlands — Ministry of Education, Culture and Science; Netherlands Organisation for Scientific Research (NWO); Dutch national e-infrastructure with the support of SURF Cooperative; Poland — Ministry of Education and Science, grant No. DIR/WK/2018/11; National Science Centre, Grants No. 2016/22/M/ST9/00198, 2016/23/B/ST9/01635, and 2020/39/B/ST9/01398; Portugal — Portuguese national funds and FEDER funds within Programa Operacional Factores de Competitividade through Fundação para a Ciência e a Tecnologia (COMPETE); Romania — Ministry of Research, Innovation and Digitization, CNCS/CCCDI — UEFISCDI, projects PN19150201/16N/2019, PN1906010, TE128 and PED289, within PNCDI III; Slovenia — Slovenian Research Agency, grants P1-0031, P1-0385, I0-0033, N1-0111; Spain — Ministerio de Economía, Industria y Competitividad (FPA2017-85114-P and PID2019-104676GB-C32), Xunta de Galicia (ED431C 2017/07), Junta de Andalucía (SOMM17/6104/UGR, P18-FR-4314) Feder Funds, RENATA Red Nacional Temática de Astropartículas (FPA2015-68783-REDT) and María de Maeztu Unit of Excellence (MDM-2016-0692); U.S.A. — 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; Marie Curie-IRSES/EPLANET; European Particle Physics Latin American Network; and UNESCO.Lorentz invariance violation (LIV) is often described by dispersion relations of the form E i2 = m i2+p i2+δi,n E 2+n with delta different based on particle type i, with energy E, momentum p and rest mass m. Kinematics and energy thresholds of interactions are modified once the LIV terms become comparable to the squared masses of the particles involved. Thus, the strongest constraints on the LIV coefficients δi,n tend to come from the highest energies. At sufficiently high energies, photons produced by cosmic ray interactions as they propagate through the Universe could be subluminal and unattenuated over cosmological distances. Cosmic ray interactions can also be modified and lead to detectable fingerprints in the energy spectrum and mass composition observed on Earth. The data collected at the Pierre Auger Observatory are therefore possibly sensitive to both the electromagnetic and hadronic sectors of LIV. In this article, we explore these two sectors by comparing the energy spectrum and the composition of cosmic rays and the upper limits on the photon flux from the Pierre Auger Observatory with simulations including LIV. Constraints on LIV parameters depend strongly on the mass composition of cosmic rays at the highest energies. For the electromagnetic sector, while no constraints can be obtained in the absence of protons beyond 1019 eV, we obtain δγ,0 > -10-21, δγ,1 > -10-40 eV-1 and δγ,2 > -10-58 eV-2 in the case of a subdominant proton component up to 1020 eV. For the hadronic sector, we study the best description of the data as a function of LIV coefficients and we derive constraints in the hadronic sector such as δhad,0 < 10-19, δhad,1 < 10-38 eV-1 and δhad,2 < 10-57 eV-2 at 5σ CL.Argentina — Comisión Nacional de Energía AtómicaAgencia Nacional de Promoción Científica y Tecnológica (ANPCyT)Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)Gobierno de la Provincia de MendozaMunicipalidad de MalargüeNDM Holdings and Valle Las LeñasAustralia — the Australian Research CouncilBelgium — Fonds de la Recherche Scientifique (FNRS)Research Foundation Flanders (FWO)Brazil — Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)Financiadora de Estudos e Projetos (FINEP)Fundação de Amparo à Pesquisa do Estado de Rio de Janeiro (FAPERJ)São Paulo Research Foundation (FAPESP) Grants No. 2019/10151-2, No. 2010/07359-6 and No. 1999/05404-3Ministério da Ciência, Tecnologia, Inovações e Comunicações (MCTIC)Czech Republic — Grant No. MSMT CR LTT18004, LM2015038, LM2018102, CZ.02.1.01/0.0/0.0/16_013/0001402, CZ.02.1.01/0.0/0.0/18_046/0016010 and CZ.02.1.01/0.0/0.0/17_049/0008422France — Centre de Calcul IN2P3/CNRSCentre National de la Recherche Scientifique (CNRS)Conseil Régional Ile-de-France; Département Physique Nucléaire et Corpusculaire (PNC-IN2P3/CNRS)Département Sciences de l’Univers (SDU-INSU/CNRS)Institut Lagrange de Paris (ILP) Grant No. LABEX ANR-10-LABX-63- Investissements d’Avenir Programme Grant No. ANR-11-IDEX-0004-02Germany — Bundesministerium für Bildung und Forschung (BMBF)GermanyDeutsche Forschungsgemeinschaft (DFG)Finanzministerium Baden-WürttembergHelmholtz Alliance for Astroparticle Physics (HAP)Helmholtz-Gemeinschaft Deutscher Forschungszentren (HGF)Ministerium für Innovation, Wissenschaft und Forschung des Landes Nordrhein-WestfalenMinisterium für Wissenschaft, Forschung und Kunst des Landes Baden-WürttembergItaly — Istituto Nazionale di Fisica Nucleare (INFN)Istituto Nazionale di Astrofisica (INAF)Ministero dell’Istruzione, dell’Università e della Ricerca (MIUR)CETEMPS Center of ExcellenceMinistero degli Affari Esteri (MAE)México — Consejo Nacional de Ciencia y Tecnología (CONACYT) No. 167733Universidad Nacional Autónoma de México (UNAM)PAPIIT DGAPA-UNAMThe Netherlands — Ministry of Education, Culture and ScienceNetherlands Organisation for Scientific Research (NWO)Dutch national e-infrastructure with the support of SURF Cooperative; Poland — Ministry of Education and Science, grant No. DIR/WK/2018/11National Science Centre, Grants No. 2016/22/M/ST9/00198, 2016/23/B/ST9/01635, and 2020/39/B/ST9/01398Portugal — Portuguese national funds and FEDER funds within Programa Operacional Factores de Competitividade through Fundação para a Ciência e a Tecnologia (COMPETE)Romania — Ministry of Research, Innovation and Digitization, CNCS/CCCDI — UEFISCDI, projects PN19150201/16N/2019, PN1906010, TE128 and PED289, within PNCDI IIISlovenia — Slovenian Research Agency, grants P1-0031, P1-0385, I0-0033, N1-0111Spain — Ministerio de Economía, Industria y Competitividad (FPA2017-85114-P and PID2019-104676GB-C32)Xunta de Galicia (ED431C 2017/07)Junta de Andalucía (SOMM17/6104/UGR, P18-FR-4314)Feder FundsRENATA Red Nacional Temática de Astropartículas (FPA2015-68783-REDT)María de Maeztu Unit of Excellence (MDM-2016-0692)U.S.A. — Department of Energy, Contracts No. DE-AC02-07CH11359, No. DE-FR02-04ER41300, No. DE-FG02-99ER41107 and No. DE-SC0011689National Science Foundation, Grant No. 0450696The Grainger FoundationMarie Curie-IRSES/EPLANETEuropean Particle Physics Latin American NetworkUNESC

Searches for Ultra-High-Energy Photons at the Pierre Auger Observatory

The Pierre Auger Observatory, which is the largest air-shower experiment in the world, offers unprecedented exposure to neutral particles at the highest energies. Since the start of data collection more than 18 years ago, various searches for ultra-high-energy (UHE, E & 1017 eV) photons have been performed, either for a diffuse flux of UHE photons, for point sources of UHE photons or for UHE photons associated with transient events such as gravitational wave events. In the present paper, we summarize these searches and review the current results obtained using the wealth of data collected by the Pierre Auger Observatory.Argentina-Comision Nacional de Energia AtomicaANPCyTConsejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET)Gobierno de la Provincia de MendozaMunicipalidad de MalargueNDM HoldingsValle Las LenasAustralian Research CouncilBelgium-Fonds de la Recherche Scientifique (FNRS)FWOConselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPQ) Fundacao de Apoio a Pesquisa do Distrito Federal (FAPDF) Financiadora de Inovacao e Pesquisa (Finep) Fundacao Carlos Chagas Filho de Amparo a Pesquisa do Estado do Rio De Janeiro (FAPERJ) Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP) 2019/10151-2 2010/07359-6 1999/05404-3Ministerio da Ciencia, Tecnologia, Inovacoes e Comunicacoes (MCTIC)France-Centre de Calcul IN2P3/CNRS Centre National de la Recherche Scientifique (CNRS) Region Ile-de-France Centre National de la Recherche Scientifique (CNRS) Departement Sciences de l'Univers (SDU-INSU/CNRS) French National Research Agency (ANR) LABEX ANR-10-LABX-63 ANR-11-IDEX-0004-02Federal Ministry of Education & Research (BMBF) German Research Foundation (DFG) Finanzministerium Baden-Wurttemberg Helmholtz Alliance for Astroparticle Physics (HAP) Helmholtz Association Ministerium fur Kultur und Wissenschaft des Landes Nordrhein-Westfalen Ministerium fur Wissenschaft, Forschung und Kunst des Landes Baden-WurttembergItaly-Istituto Nazionale di Fisica Nucleare (INFN) Istituto Nazionale Astrofisica (INAF)Ministry of Education, Universities and Research (MIUR)CETEMPS Center of ExcellenceMinistry of Foreign Affairs and International Cooperation (Italy)Consejo Nacional de Ciencia y Tecnologia (CONACyT) 167733 Universidad Nacional Autonoma de Mexico Programa de Apoyo a Proyectos de Investigacion e Innovacion Tecnologica (PAPIIT) Universidad Nacional Autonoma de MexicoNetherlands-Ministry of Education, Culture and Science Netherlands Organization for Scientific Research (NWO)SURF CooperativePoland-Ministry of Education and Science DIR/WK/2018/11 National Science Centre, Poland 2016/22/M/ST9/00198 2016/23/B/ST9/01635 2020/39/B/ST9/01398Portuguese Foundation for Science and Technology FEDER funds within Programa Operacional Factores de Competitividade through FundacAo para a Ciencia e a Tecnologia (COMPETE)Romania-Ministry of Research, Innovation and Digitization, CNCS/CCCDI UEFISCDI within the National Nucleus Program PN19150201/16N/2019 PN1906010 PNCDI III TE128 PN-III-P1-1.1-TE-2021-0924/TE57/2022 PED289Slovenian Research Agency - Slovenia P1-0031 P1-0385 I0-0033 N1-0111Spanish Government FPA2017-85114-P PID2019-104676GB-C32Xunta de GaliciaEuropean Commission ED431C 2017/07Junta de Andalucia SOMM17/6104/UGR P18-FR-4314European CommissionRENATA Red Nacional Tematica de Astroparticulas FPA2015-68783-REDTMaria de Maeztu Unit of Excellence MDM-2016-0692United States Department of Energy (DOE) DE-AC02-07CH11359 DE-FR02-04ER41300 DE-FG02-99ER41107 DE-SC0011689National Science Foundation (NSF) 0450696Grainger FoundationMarie Curie-IRSES/EPLANETEuropean Particle Physics Latin American NetworkUNESCOMSMT CR LTT18004 LM2015038 LM2018102 CZ.02.1.01/0.0/0.0/16_013/0001402 CZ.02.1.01/0.0/0.0/18_046/0016010 CZ.02.1.01/0.0/0.0/17_049/000842

Arrival Directions of Cosmic Rays above 32 EeV from Phase One of the Pierre Auger Observatory

A promising energy range to look for angular correlations between cosmic rays of extragalactic origin and their sources is at the highest energies, above a few tens of EeV (1 EeV ≡ 1018 eV). Despite the flux of these particles being extremely low, the area of ∼3000 km2 covered at the Pierre Auger Observatory, and the 17 yr data-taking period of the Phase 1 of its operations, have enabled us to measure the arrival directions of more than 2600 ultrahigh- energy cosmic rays above 32 EeV. We publish this data set, the largest available at such energies from an integrated exposure of 122,000 km2 sr yr, and search it for anisotropies over the 3.4π steradians covered with the Observatory. Evidence for a deviation in excess of isotropy at intermediate angular scales, with ∼15° Gaussian spread or ∼25° top-hat radius, is obtained at the 4σ significance level for cosmic-ray energies above ∼40 EeV.Argentina-Comision Nacional de Energia AtomicaANPCyTConsejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET)Fundacao de Amparo a Pesquisa do Estado de Sao Paulo (FAPESP) 2019/10151-2 2010/07359-6 1999/05404-3Ministry of Education, Youth & Sports - Czech Republic LTT18004 LM2015038 LM2018102 CZ.02.1.01/0.0/0.0/16_013/0001402 CZ.02.1.01/0.0/0.0/18_046/0016010 CZ.02.1.01/0.0/0.0/17_049/0008422French National Research Agency (ANR) LABEX ANR-10-LABX-63 ANR-11-IDEX-0004-02Consejo Nacional de Ciencia y Tecnologia (CONACyT) 167733Netherlands Organization for Scientific Research (NWO) DIR/WK/2018/11National Science Centre, Poland 2016/22/M/ST9/00198 2016/23/B/ST9/01635 2020/39/B/ST9/01398Romania-Ministry of Research, Innovation and Digitization, CNCS/CCCDIUEFISCDI within PNCDI III PN19150201/16N/2019 PN1906010 TE128 PED289Slovenian Research Agency - Slovenia P1-0031 P1-0385 I0-0033 N1-0111Spanish Government FPA2017-85114-P PID2019-104676GB-C32Xunta de GaliciaEuropean Commission ED431C 2017/07Junta de Andalucia Feder Funds SOMM17/6104/UGR P18-FR-4314RENATA Red Nacional Tematica de Astroparticulas FPA2015-68783-REDTMaria de Maeztu Unit of Excellence MDM-2016-0692United States Department of Energy (DOE) DE-AC02-07CH11359 DE-FR02-04ER41300 DE-FG02-99ER41107 DE-SC0011689National Science Foundation (NSF) 0450696Gobierno de la Provincia de MendozaMunicipalidad de MalargueNDM Holdings and Valle Las LenasAustralian Research CouncilBelgium -Fonds de la Recherche Scientifique (FNRS)FWOConselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPQ)Fundacao de Apoio a Pesquisa do Distrito Federal (FAPDF)Financiadora de Inovacao e Pesquisa (Finep)Fundacao Carlos Chagas Filho de Amparo a Pesquisa do Estado do Rio De Janeiro (FAPERJ)Ministerio da Ciencia, Tecnologia, Inovacoes e Comunicacoes (MCTIC)France-Centre de Calcul IN2P3/CNRSFrance-Centre de Calcul IN2P3/CNRS Centre National de la Recherche Scientifique (CNRS) Departement Sciences de l'Univers (SDU-INSU/CNRS)Federal Ministry of Education & Research (BMBF) German Research Foundation (DFG) Finanzministerium Baden-Wurttemberg Helmholtz Alliance for Astroparticle Physics (HAP) Helmholtz Association Ministerium fur Innovation, Wissenschaft und Forschung des Landes Nordrhein-Westfalen Ministerium fur Wissenschaft, Forschung und Kunst des Landes Baden-WurttembergItaly-Istituto Nazionale di Fisica Nucleare (INFN)Istituto Nazionale Astrofisica (INAF)Ministry of Education, Universities and Research (MIUR)CETEMPS Center of ExcellenceMinistry of Foreign Affairs and International Cooperation (Italy)Universidad Nacional Autonoma de MexicoPrograma de Apoyo a Proyectos de Investigacion e Innovacion Tecnologica (PAPIIT)Universidad Nacional Autonoma de MexicoNetherlands-Ministry of Education, Culture and Science Netherlands Organization for Scientific Research (NWO)SURF CooperativePortuguese Foundation for Science and TechnologyFEDER funds within Programa Operacional Factores de Competitividade through Fundacao para a Ciencia e a Tecnologia (COMPETE)The Grainger Foundation xMarie Curie-IRSES/EPLANETEuropean Particle Physics Latin American NetworkUNESC

Measurement of the energy spectrum of cosmic rays above 10(18) eV using the Pierre Auger Observatory

We report a measurement of the flux of cosmic rays with unprecedented precision and Statistics using the Pierre Auger Observatory Based on fluorescence observations in coincidence with at least one Surface detector we derive a spectrum for energies above 10(18) eV We also update the previously published energy spectrum obtained with the surface detector array The two spectra are combined addressing the systematic uncertainties and, in particular. the influence of the energy resolution on the spectral shape The spectrum can be described by a broken power law E-gamma with index gamma = 3 3 below the ankle which is measured at log(10)(E-ankle/eV) = 18 6 Above the ankle the spectrum is described by a power law with index 2 6 followed by a flux suppression, above about log(10)(E/eV) = 19 5, detected with high statistical significance.The successful installation and commissioning of the Pierre Auger Observatory would not have been possible without the strong commitment and effort from the technical and administrative staff in Malargüe. We are very grateful to the following agencies and organizations for financial support: Comisión Nacional de Energía Atómica, Fundación Antorchas, Gobierno De La Provincia de Mendoza, Municipalidad de Malargüe, NDM Holdings and Valle Las Leñas, in gratitude for their continuing cooperation over land access, Argentina; the Australian Research Council; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), Financiadora de Estudos e Projetos (FINEP), Fundaçao de Amparo à Pesquisa do Estado de Rio de Janeiro (FAPERJ), Fundaçao de Amparo à Pesquisa do Estado de Sao Paulo (FAPESP), Ministério de Ciência e Tecnologia (MCT), Brazil; AVCR AV0Z10100502 and AV0Z10100522, GAAV KJB300100801 and KJB100100904, MSMT-CR LA08016, LC527, 1M06002, and MSM0021620859, Czech Republic; Centre de Calcul IN2P3/CNRS, Centre National de la Recherche Scientifique (CNRS), Conseil Régional Ile-de-France, Département Physique Nucléaire et Corpusculaire (PNC-IN2P3/CNRS), Département Sciences de l’Univers (SDU-INSU/CNRS), France; Bundesministerium für Bildung und Forschung (BMBF), Deutsche Forschungsgemeinschaft (DFG), Finanzministerium Baden- Württemberg, Helmholtz-Gemeinschaft Deutscher Forschungszentren (HGF), Ministerium für Wissenschaft und Forschung, Nordrhein-Westfalen, Ministerium für Wissenschaft, Forschung und Kunst, Baden-Württemberg, Germany; Istituto Nazionale di Fisica Nucleare (INFN), Ministero dell’Istruzione,dell’Università e della Ricerca (MIUR), Italy; Consejo Nacional de Ciencia y Tecnología (CONACYT), Mexico; Ministerie van Onderwijs, Cultuur en Wetenschap, Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO), Stichting voor Fundamenteel Onderzoek der Materie (FOM), Netherlands; Ministry of Science and Higher Education, Grant Nos. 1 P03 D 014 30, N202 090 31/0623, and PAP/218/2006, Poland; Fundaçao para a Ciência e a Tecnologia, Portugal; Ministry for Higher Education, Science, and Technology, Slovenian Research Agency, Slovenia; Comunidad de Madrid, Consejería de Educación de la Comunidad de Castilla La Mancha, FEDER funds, Ministerio de Ciencia e Innovación, Xunta de Galicia, Spain; Science and Technology Facilities Council, United Kingdom; Department of Energy, Contract No. DE-AC02-07CH11359, National Science Foundation, Grant No. 0450696, The Grainger Foundation USA; ALFA-EC / HELEN, European Union 6th Framework Program, Grant No. MEIF-CT-2005-025057, European Union 7th Framework Program, Grant No. PIEF-GA-2008-220240, and UNESCO.Peer reviewe

Search for ultrahigh energy neutrinos in highly inclined events at the Pierre Auger Observatory

The Surface Detector of the Pierre Auger Observatory is sensitive to neutrinos of all flavors above 0.1 EeV. These interact through charged and neutral currents in the atmosphere giving rise to extensive air showers. When interacting deeply in the atmosphere at nearly horizontal incidence, neutrinos can be distinguished from regular hadronic cosmic rays by the broad time structure of their shower signals in the water-Cherenkov detectors. In this paper we present for the first time an analysis based on down-going neutrinos. We describe the search procedure, the possible sources of background, the method to compute the exposure and the associated systematic uncertainties. No candidate neutrinos have been found in data collected from 1 January 2004 to 31 May 2010. Assuming an E-2 differential energy spectrum the limit on the single-flavor neutrino is E2dN=dE-7GeVcm-2s-1sr-1 at 90% C.L. in the energy range 1 X 1017eV\u3c E 1020eV

Origin of atmospheric aerosols at the Pierre Auger Observatory using backward trajectory of air masses

The Pierre Auger Observatory is the largest operating cosmic ray observatory ever built. Calorimetric measurements of extensive air showers induced by cosmic rays are performed with a fluorescence detector. Thus, one of the main challenges is the monitoring of the atmosphere, both in terms of atmospheric state variables and optical properties. To better understand the atmospheric conditions, a study of air mass trajectories above the site is presented. Such a study has been done using an air-modelling program well known in atmospheric sciences. Its validity has been checked using meteorological radiosonde soundings performed at the Pierre Auger Observatory. Finally, aerosol concentration values measured by the Central Laser Facility are compared to backward trajectories.Comment: 4 pages, 6 figures -- ECRS'12 European Cosmic Ray Symposium (July, 3-7, 2012) at Moscow, Russi

Search for point-like sources of ultra-high energy neutrinos at the Pierre Auger Observatory and improved limit on the diffuse flux of tau neutrinos

The Surface Detector array of the Pierre Auger Observatory can detect neutrinos with energy between 10^17 eV and 10^20 eV from point-like sources across the sky south of +55 deg and north of -65 deg declinations. A search has been performed for highly inclined extensive air showers produced by the interaction of neutrinos of all flavours in the atmosphere (downward-going neutrinos), and by the decay of tau leptons originating from tau neutrinos interactions in the Earth's crust (Earth-skimming neutrinos). No candidate neutrinos have been found in data up to 2010 May 31. This corresponds to an equivalent exposure of ~3.5 years of a full surface detector array for the Earth-skimming channel and ~2 years for the downward-going channel. An improved upper limit on the diffuse flux of tau neutrinos has been derived. Upper limits on the neutrino flux from point-like sources have been derived as a function of the source declination. Assuming a differential neutrino flux k_PS E^-2 from a point-like source, 90% C.L. upper limits for k_PS at the level of ~5 x 10^-7 and 2.5 x 10^-6 GeV cm^-2 s^-1 have been obtained over a broad range of declinations from the searches of Earth-skimming and downward-going neutrinos, respectively.Peer Reviewe

A Search for Point Sources of EeV Neutrons

A thorough search of the sky exposed at the Pierre Auger Cosmic Ray Observatory reveals no statistically significant excess of events in any small solid angle that would be indicative of a flux of neutral particles from a discrete source. The search covers from -90 to +15 degrees in declination using four different energy ranges above 1 EeV (10^18 eV). The method used in this search is more sensitive to neutrons than to photons. The upper limit on a neutron flux is derived for a dense grid of directions for each of the four energy ranges. These results constrain scenarios for the production of ultra-high energy cosmic rays in the Galaxy.Peer Reviewe