A targeted search for point sources of EeV photons with the Pierre Auger Observatory

We report a first measurement for ultrahigh energy cosmic rays of the correlation between the depth of shower maximum and the signal in the water Cherenkov stations of air-showers registered simultaneously by the fluorescence and the surface detectors of the Pierre Auger Observatory. Such a correlation measurement is a unique feature of a hybrid air-shower observatory with sensitivity to both the electromagnetic and muonic components. It allows an accurate determination of the spread of primary masses in the cosmic-ray flux. Up till now, constraints on the spread of primary masses have been dominated by systematic uncertainties. The present correlation measurement is not affected by systematics in the measurement of the depth of shower maximum or the signal in the water Cherenkov stations. The analysis relies on general characteristics of air showers and is thus robust also with respect to uncertainties in hadronic event generators. The observed correlation in the energy range around the 'ankle' at lg(E/eV) = 18.5-19.0 differs significantly from expectations for pure primary cosmic-ray compositions. A light composition made up of proton and helium only is equally inconsistent with observations. The data are explained well by a mixed composition including nuclei with mass A > 4. Scenarios such as the proton dip model, with almost pure compositions, are thus disfavored as the sole explanation of the ultrahigh-energy cosmic-ray flux at Earth. (C) 2016 The Author(s). Published by Elsevier B.V

Search for ultrarelativistic magnetic monopoles with the Pierre Auger observatory

We present a search for ultrarelativistic magnetic monopoles with the Pierre Auger observatory. Such particles, possibly a relic of phase transitions in the early Universe, would deposit a large amount of energy along their path through the atmosphere, comparable to that of ultrahigh-energy cosmic rays (UHECRs). The air-shower profile of a magnetic monopole can be effectively distinguished by the fluorescence detector from that of standard UHECRs. No candidate was found in the data collected between 2004 and 2012, with an expected background of less than 0.1 event from UHECRs. The corresponding 90% confidence level (C.L.) upper limits on the flux of ultrarelativistic magnetic monopoles range from 10(-1)9 (cm(2) sr s)(-1) for a Lorentz factor gamma = 10(9) to 2.5 x 10(-21) (cm(2) sr s)(-1) for gamma = 10(12). These results-the first obtained with a UHECR detector-improve previously published limits by up to an order of magnitude

Impact of atmospheric effects on the energy reconstruction of air showers observed by the surface detectors of the Pierre Auger Observatory

Atmospheric conditions, such as the pressure (P), temperature (T) or air density (rho proportional to P/T), affect the development of extended air showers initiated by energetic cosmic rays. We study the impact of the atmospheric variations on the reconstruction of air showers with data from the arrays of surface detectors of the Pierre Auger Observatory, considering separately the one with detector spacings of 1500m and the one with 750m spacing. We observe modulations in the event rates that are due to the influence of the air density and pressure variations on the measured signals, from which the energy estimators are obtained. We show how the energy assignment can be corrected to account for such atmospheric effects

Combined fit of spectrum and composition data as measured by the Pierre Auger Observatory

We present a combined fit of a simple astrophysical model of UHECR sources to both the energy spectrum and mass composition data measured by the Pierre Auger Observatory. The fit has been performed for energies above 5.10(18) eV, i.e. the region of the all-particle spectrum above the so-called "ankle" feature. The astrophysical model we adopted consists of identical sources uniformly distributed in a comoving volume, where nuclei are accelerated through a rigidity-dependent mechanism. The fit results suggest sources characterized by relatively low maximum injection energies, hard spectra and heavy chemical composition. We also show that uncertainties about physical quantities relevant to UHECR propagation and shower development have a non-negligible impact on the fit results

Combined fit of spectrum and composition data as measured by the Pierre Auger Observatory (vol 4, 038, 2017) (Erratum)

© Iop Publishing. Artículo firmado por más de 10 autores.Depto. de Estructura de la Materia, Física Térmica y ElectrónicaFac. de Ciencias FísicasTRUEpu

Ultrahigh-energy neutrino follow-up of gravitational wave events GW150914 and GW151226 with the Pierre Auger Observatory

© 2016 American Physical Society. Artículo firmado por más de 10 autores. 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, Agencia Nacional de Promocion Cientifica y Tecnologica (ANPCyT), Consejo Nacional de Investigaciones Cientificas y Tecnicas (CONICET), 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 and No. 1999/05404-3, Ministerio de Ciencia e Tecnologia (MCT), Brazil, Grants No. MSMT CR LG15014, No. LO1305, and No. LM2015038; 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) Grant No. LABEX ANR-10-LABX-63, within the Investissements d'Avenir Programme Grant No. ANR-11-IDEX-0004-02, France; Bundesministerium fur Bildung und Forschung (BMBF), Deutsche Forschungsgemeinschaft (DFG), Finanzministerium Baden-Wurttemberg, Helmholtz Alliance for Astroparticle Physics (HAP), 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), Istituto Nazionale di Astrofisica (INAF), Ministero dell'Istruzione, dell'Universita e della Ricerca (MIUR), Gran Sasso Center for Astroparticle Physics (CFA), CETEMPS Center of Excellence, Ministero degli Affari Esteri (MAE), Italy; Consejo Nacional de Ciencia y Tecnologia (CONACYT) Grant No. 167733, Mexico; Universidad Nacional Autonoma de Mexico (UNAM), Grant No. PAPIIT DGAPA-UNAM, 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 Programa Operacional Factores de Competitividade through Fundacao para a Ciencia e a Tecnologia (COMPETE), Portugal; Romanian Authority for Scientific Research ANCS, CNDI-UEFISCDI partnership projects Grants No. 20/2012, No. 194/2012, and No. PN 16 42 01 02; Slovenian Research Agency, Slovenia; Comunidad de Madrid, Fondo Europeo de Desarrollo Regional (FEDER) funds, Ministerio de Economia y Competitividad, Xunta de Galicia, European Community 7th Framework Program, Grant No. FP7-PEOPLE-2012-IEF-328826, Spain; Science and Technology Facilities Council, United Kingdom; 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.On September 14, 2015 the Advanced LIGO detectors observed their first gravitational wave (GW) transient GW150914. This was followed by a second GW event observed on December 26, 2015. Both events were inferred to have arisen from the merger of black holes in binary systems. Such a system may emit neutrinos if there are magnetic fields and disk debris remaining from the formation of the two black holes. With the surface detector array of the Pierre Auger Observatory we can search for neutrinos with energy E-nu above 100 PeV from pointlike sources across the sky with equatorial declination from about -65 degrees to +60 degrees, and, in particular, from a fraction of the 90% confidence-level inferred positions in the sky of GW150914 and GW151226. A targeted search for highly inclined extensive air showers, produced either by interactions of downward-going neutrinos of all flavors in the atmosphere or by the decays of tau leptons originating from tau-neutrino interactions in the Earth's crust (Earth-skimming neutrinos), yielded no candidates in the Auger data collected within +/- 500 s around or 1 day after the coordinated universal time (UTC) of GW150914 and GW151226, as well as in the same search periods relative to the UTC time of the GW candidate event LVT151012. From the nonobservation we constrain the amount of energy radiated in ultrahigh-energy neutrinos from such remarkable events.Depto. de Estructura de la Materia, Física Térmica y ElectrónicaFac. de Ciencias FísicasTRUEUnión Europea. FP7Ministerio de Economía y Competitividad (MINECO)Comunidad de MadridCzech Science Foundation, Czech RepublicCentre de Calcul IN2P3/CNRSCentre National de la Recherche Scientifique (CNRS)Conseil Regional Ile-de-FranceDepartement Physique Nucleaire et Corpusculaire (PNC-IN2P3/CNRS)Departement Sciences de l'Univers (SDU-INSU/CNRS)Institut Lagrange de Paris (ILP) within the Investissements d'Avenir Programme, FranceBundesministerium fur Bildung und Forschung (BMBF)Deutsche Forschungsgemeinschaft (DFG)Finanzministerium Baden-WurttembergHelmholtz Alliance for Astroparticle Physics (HAP)Helmholtz-Gemeinschaft Deutscher Forschungszentren (HGF)Ministerium fur Wissenschaft und Forschung Nordrhein WestfalenMinisterium fur Wissenschaft, Forschung und KunstBaden-Wurttembe GermanyIstituto Nazionale di Fisica Nucleare (INFN)Istituto Nazionale di Astrofisica (INAF)Ministero dell'Istruzione, dell'Universita e della Ricerca (MIUR)Gran Sasso Center for Astroparticle Physics (CFA)CETEMPS Center of ExcellenceMinistero degli Affari Esteri (MAE), ItalyMinisterie van Onderwijs, Cultuur en WetenschapNederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO)Stichting voor Fundamenteel Onderzoek der Materie (FOM)NetherlandsNational Centre for Research and DevelopmentNational Science Centre, PolandPortuguese national fundsFEDER funds within Programa Operacional Factores de Competitividade through Fundacao para a Ciencia e a Tecnologia (COMPETE), PortugalRomanian Authority for Scientific Research ANCS, CNDI-UEFISCDI partnership projectsSlovenian Research Agency, SloveniaFondo Europeo de Desarrollo Regional (FEDER) fundsXunta de GaliciaScience and Technology Facilities Council, United KingdomMarie Curie-IRSES/EPLANETEuropean Particle Physics Latin American Networkpu

Measurement of the radiation energy in the radio signal of extensive air showers as a universal estimator of cosmic-ray energy.

We measure the energy emitted by extensive air showers in the form of radio emission in the frequency range from 30 to 80 MHz. Exploiting the accurate energy scale of the Pierre Auger Observatory, we obtain a radiation energy of 15.8 +/- 0.7 (stat) +/- 6.7 (syst) MeV for cosmic rays with an energy of 1 EeV arriving perpendicularly to a geomagnetic field of 0.24 G, scaling quadratically with the cosmic-ray energy. A comparison with predictions from state-of-the-art first-principles calculations shows agreement with our measurement. The radiation energy provides direct access to the calorimetric energy in the electromagnetic cascade of extensive air showers. Comparison with our result thus allows the direct calibration of any cosmic-ray radio detector against the well-established energy scale of the Pierre Auger Observatory