The energy spectrum of cosmic rays beyond the turn-down around 10^17 eV as measured with the surface detector of the Pierre Auger Observatory

We present a measurement of the cosmic-ray spectrum above 100 PeV using the part of the surface detector of the Pierre Auger Observatory that has a spacing of 750 m. An inflection of the spectrum is observed, confirming the presence of the so-called second-knee feature. The spectrum is then combined with that of the 1500 m array to produce a single measurement of the flux, linking this spectral feature with the three additional breaks at the highest energies. The combined spectrum, with an energy scale set calorimetrically via fluorescence telescopes and using a single detector type, results in the most statistically and systematically precise measurement of spectral breaks yet obtained. These measurements are critical for furthering our understanding of the highest energy cosmic rays

Reconstruction of events recorded with the surface detector of the Pierre Auger Observatory

Cosmic rays arriving at Earth collide with the upper parts of the atmosphere, thereby inducing extensive air showers. When secondary particles from the cascade arrive at the ground, they are measured by surface detector arrays. We describe the methods applied to the measurements of the surface detector of the Pierre Auger Observatory to reconstruct events with zenith angles less than 60o using the timing and signal information recorded using the water-Cherenkov detector stations. In addition, we assess the accuracy of these methods in reconstructing the arrival directions of the primary cosmic ray particles and the sizes of the induced showers

The FRAM robotic telescope for atmospheric monitoring at the Pierre Auger Observatory

FRAM (F/Photometric Robotic Atmospheric Monitor) is a robotic telescope operated at the Pierre Auger Observatory in Argentina for the purposes of atmospheric monitoring using stellar photometry. As a passive system which does not produce any light that could interfere with the observations of the fluorescence telescopes of the observatory, it complements the active monitoring systems that use lasers. We discuss the applications of stellar photometry for atmospheric monitoring at optical observatories in general and the particular modes of operation employed by the Auger FRAM. We describe in detail the technical aspects of FRAM, the hardware and software requirements for a successful operation of a robotic telescope for such a purpose and their implementation within the FRAM system

Search for photons above 1019^{19} eV with the surface detector of the Pierre Auger Observatory

International audienceWe use the surface detector of the Pierre Auger Observatory to search for air showers initiated by photons with an energy above $10^{19}$ eV. Photons in the zenith angle range from 30$^\circ$ to 60$^\circ$ can be identified in the overwhelming background of showers initiated by charged cosmic rays through the broader time structure of the signals induced in the water-Cherenkov detectors of the array and the steeper lateral distribution of shower particles reaching ground. Applying the search method to data collected between January 2004 and June 2020, upper limits at 95% CL are set to an $E^{-2}$ diffuse flux of ultra-high energy photons above $10^{19}$ eV, $2{\times}10^{19}$ eV and $4{\times}10^{19}$ eV amounting to $2.11{\times}10^{-3}$, $3.12{\times}10^{-4}$ and $1.72{\times}10^{-4}$ km$^{-2}$ sr$^{-1}$ yr$^{-1}$, respectively. While the sensitivity of the present search around $2 \times 10^{19}$ eV approaches expectations of cosmogenic photon fluxes in the case of a pure-proton composition, it is one order of magnitude above those from more realistic mixed-composition models. The inferred limits have also implications for the search of super-heavy dark matter that are discussed and illustrated

Search for photons above 1019^{19} eV with the surface detector of the Pierre Auger Observatory

International audienceWe use the surface detector of the Pierre Auger Observatory to search for air showers initiated by photons with an energy above $10^{19}$ eV. Photons in the zenith angle range from 30$^\circ$ to 60$^\circ$ can be identified in the overwhelming background of showers initiated by charged cosmic rays through the broader time structure of the signals induced in the water-Cherenkov detectors of the array and the steeper lateral distribution of shower particles reaching ground. Applying the search method to data collected between January 2004 and June 2020, upper limits at 95% CL are set to an $E^{-2}$ diffuse flux of ultra-high energy photons above $10^{19}$ eV, $2{\times}10^{19}$ eV and $4{\times}10^{19}$ eV amounting to $2.11{\times}10^{-3}$, $3.12{\times}10^{-4}$ and $1.72{\times}10^{-4}$ km$^{-2}$ sr$^{-1}$ yr$^{-1}$, respectively. While the sensitivity of the present search around $2 \times 10^{19}$ eV approaches expectations of cosmogenic photon fluxes in the case of a pure-proton composition, it is one order of magnitude above those from more realistic mixed-composition models. The inferred limits have also implications for the search of super-heavy dark matter that are discussed and illustrated

Search for photons above 1019^{19} eV with the surface detector of the Pierre Auger Observatory

We use the surface detector of the Pierre Auger Observatory to search for air showers initiated by photons with an energy above $10^{19}$ eV. Photons in the zenith angle range from 30$^\circ$ to 60$^\circ$ can be identified in the overwhelming background of showers initiated by charged cosmic rays through the broader time structure of the signals induced in the water-Cherenkov detectors of the array and the steeper lateral distribution of shower particles reaching ground. Applying the search method to data collected between January 2004 and June 2020, upper limits at 95% CL are set to an $E^{-2}$ diffuse flux of ultra-high energy photons above $10^{19}$ eV, $2{\times}10^{19}$ eV and $4{\times}10^{19}$ eV amounting to $2.11{\times}10^{-3}$, $3.12{\times}10^{-4}$ and $1.72{\times}10^{-4}$ km$^{-2}$ sr$^{-1}$ yr$^{-1}$, respectively. While the sensitivity of the present search around $2 \times 10^{19}$ eV approaches expectations of cosmogenic photon fluxes in the case of a pure-proton composition, it is one order of magnitude above those from more realistic mixed-composition models. The inferred limits have also implications for the search of super-heavy dark matter that are discussed and illustrated

Search for magnetically-induced signatures in the arrival directions of ultra-high-energy cosmic rays measured at the Pierre Auger Observatory

We search for signals of magnetically-induced effects in the arrival directions of ultra-high-energy cosmic rays detected at the Pierre Auger Observatory. We apply two different methods. One is a search for sets of events that show a correlation between their arrival direction and the inverse of their energy, which would be expected if they come from the same point-like source, they have the same electric charge and their deflection is relatively small and coherent. We refer to these sets of events as "multiplets". The second method, called "thrust", is a principal axis analysis aimed to detect the elongated patterns in a region of interest. We study the sensitivity of both methods using a benchmark simulation and we apply them to data in two different searches. The first search is done assuming as source candidates a list of nearby active galactic nuclei and starburst galaxies. The second is an all-sky blind search. We report the results and we find no statistically significant features. We discuss the compatibility of these results with the indications on the mass composition inferred from data of the Pierre Auger Observatory. © 2020 IOP Publishing Ltd and Sissa Medialab

Design, upgrade and characterization of the silicon photomultiplier front-end for the AMIGA detector at the Pierre Auger Observatory

none359AMIGA (Auger Muons and Infill for the Ground Array) is an upgrade of the Pierre Auger Observatory to complement the study of ultra-high-energy cosmic rays (UHECR) by measuring the muon content of extensive air showers (EAS). It consists of an array of 61 water Cherenkov detectors on a denser spacing in combination with underground scintillation detectors used for muon density measurement. Each detector is composed of three scintillation modules, with 10 m(2) detection area per module, buried at 2.3 m depth, resulting in a total detection area of 30 m(2). Silicon photomultiplier sensors (SiPM) measure the amount of scintillation light generated by charged particles traversing the modules. In this paper, the design of the front-end electronics to process the signals of those SiPMs and test results from the laboratory and from the Pierre Auger Observatory are described. Compared to our previous prototype, the new electronics shows a higher performance, higher efficiency and lower power consumption, and it has a new acquisition system with increased dynamic range that allows measurements closer to the shower core. The new acquisition system is based on the measurement of the total charge signal that the muonic component of the cosmic ray shower generates in the detector.noneAab A.; Abreu P.; Aglietta M.; Albury J.M.; Allekotte I.; Almela A.; Alvarez-Muniz J.; Alves Batista R.; Anastasi G.A.; Anchordoqui L.; Andrada B.; Andringa S.; Aramo C.; Araujo Ferreira P.R.; Asorey H.; Assis P.; Avila G.; Badescu A.M.; Bakalova A.; Balaceanu A.; Barbato F.; Barreira Luz R.J.; Becker K.H.; Bellido J.A.; Berat C.; Bertaina M.E.; Bertou X.; Biermann P.L.; Bister T.; Biteau J.; Blazek J.; Bleve C.; Bohacova M.; Boncioli D.; Bonifazi C.; Bonneau Arbeletche L.; Borodai N.; Botti A.M.; Brack J.; Bretz T.; Briechle F.L.; Buchholz P.; Bueno A.; Buitink S.; Buscemi M.; Caballero-Mora K.S.; Caccianiga L.; Canfora F.; Caracas I.; Carceller J.M.; Caruso R.; Castellina A.; Catalani F.; Cataldi G.; Cazon L.; Cerda M.; Chinellato J.A.; Choi K.; Chudoba J.; Chytka L.; Clay R.W.; Cobos Cerutti A.C.; Colalillo R.; Coleman A.; Coluccia M.R.; Conceicao R.; Condorelli A.; Consolati G.; Contreras F.; Convenga F.; Covault C.E.; Dasso S.; Daumiller K.; Dawson B.R.; Day J.A.; de Almeida R.M.; de Jesus J.; de Jong S.J.; de Mauro G.; de Mello Neto J.R.T.; de Mitri I.; de Oliveira J.; de Oliveira Franco D.; de Souza V.; de Vito E.; Debatin J.; del Rio M.; Deligny O.; Di Matteo A.; Dobrigkeit C.; D'Olivo J.C.; dos Anjos R.C.; Dova M.T.; Ebr J.; Engel R.; Epicoco I.; Erdmann M.; Escobar C.O.; Etchegoyen A.; Falcke H.; Farmer J.; Farrar G.; Fauth A.C.; Fazzini N.; Feldbusch F.; Fenu F.; Fick B.; Figueira J.M.; Filipcic A.; Fodran T.; Freire M.M.; Fujii T.; Fuster A.; Galea C.; Galelli C.; Garcia B.; Garcia Vegas A.L.; Gemmeke H.; Gesualdi F.; Gherghel-Lascu A.; Ghia P.L.; Giaccari U.; Giammarchi M.; Giller M.; Glombitza J.; Gobbi F.; Gollan F.; Golup G.; Gomez Berisso M.; Gomez Vitale P.F.; Gongora J.P.; Gonzalez J.M.; Gonzalez N.; Goos I.; Gora D.; Gorgi A.; Gottowik M.; Grubb T.D.; Guarino F.; Guedes G.P.; Guido E.; Hahn S.; Hampel M.R.; Hansen P.; Harari D.; Harvey V.M.; Haungs A.; Hebbeker T.; Heck D.; Hill G.C.; Hojvat C.; Horandel J.R.; Horvath P.; Hrabovsky M.; Huege T.; Hulsman J.; Insolia A.; Isar P.G.; Johnsen J.A.; Jurysek J.; Kaapa A.; Kampert K.H.; Keilhauer B.; Kemp J.; Klages H.O.; Kleifges M.; Kleinfeller J.; Kopke M.; Lago B.L.; Lang R.G.; Langner N.; Leigui de Oliveira M.A.; Lenok V.; Letessier-Selvon A.; Lhenry-Yvon I.; Lo Presti D.; Lopes L.; Lopez R.; Luce Q.; Lucero A.; Lundquist J.P.; Machado Payeras A.; Mancarella G.; Mandat D.; Manning B.C.; Manshanden J.; Mantsch P.; Marafico S.; Mariazzi A.G.; Maris I.C.; Marsella G.; Martello D.; Martinez H.; Martinez Bravo O.; Mastrodicasa M.; Mathes H.J.; Matthews J.; Matthiae G.; Mayotte E.; Mazur P.O.; Medina-Tanco G.; Melo D.; Menshikov A.; Merenda K.-D.; Michal S.; Micheletti M.I.; Miramonti L.; Mollerach S.; Montanet F.; Morello C.; Mostafa M.; Muller A.L.; Muller M.A.; Mulrey K.; Mussa R.; Muzio M.; Namasaka W.M.; Nellen L.; Niculescu-Oglinzanu M.; Niechciol M.; Nitz D.; Nosek D.; Novotny V.; Nozka L.; Nucita A.; Nunez L.A.; Palatka M.; Pallotta J.; Papenbreer P.; Parente G.; Parra A.; Pech M.; Pedreira F.; Pekala J.; Pelayo R.; Pena-Rodriguez J.; Perez Armand J.; Perlin M.; Perrone L.; Petrera S.; Pierog T.; Pimenta M.; Pirronello V.; Platino M.; Pont B.; Pothast M.; Privitera P.; Prouza M.; Puyleart A.; Querchfeld S.; Rautenberg J.; Ravignani D.; Reininghaus M.; Ridky J.; Riehn F.; Risse M.; Ristori P.; Rizi V.; Rodrigues de Carvalho W.; Rodriguez Rojo J.; Roncoroni M.J.; Roth M.; Roulet E.; Rovero A.C.; Ruehl P.; Saffi S.J.; Saftoiu A.; Salamida F.; Salazar H.; Salina G.; Sanabria Gomez J.D.; Sanchez F.; Santos E.M.; Santos E.; Sarazin F.; Sarmento R.; Sarmiento-Cano C.; Sato R.; Savina P.; Schafer C.M.; Scherini V.; Schieler H.; Schimassek M.; Schimp M.; Schluter F.; Schmidt D.; Scholten O.; Schovanek P.; Schroder F.G.; Schroder S.; Schulte J.; Sciutto S.J.; Scornavacche M.; Shellard R.C.; Sigl G.; Silli G.; Sima O.; Smida R.; Sommers P.; Soriano J.F.; Souchard J.; Squartini R.; Stadelmaier M.; Stanca D.; Stanic S.; Stasielak J.; Stassi P.; Streich A.; Suarez-Duran M.; Sudholz T.; Suomijarvi T.; Supanitsky A.D.; Supik J.; Szadkowski Z.; Taboada A.; Tapia A.; Timmermans C.; Tkachenko O.; Tobiska P.; Todero Peixoto C.J.; Tome B.; Travaini A.; Travnicek P.; Trimarelli C.; Trini M.; Tueros M.; Ulrich R.; Unger M.; Vaclavek L.; Vacula M.; Valdes Galicia J.F.; Valore L.; Varela E.; Varma V.K.C.; Vasquez-Ramirez A.; Veberic D.; Ventura C.; Vergara Quispe I.D.; Verzi V.; Vicha J.; Vink J.; Vorobiov S.; Wahlberg H.; Watson A.A.; Weber M.; Weindl A.; Wiencke L.; Wilczynski H.; Winchen T.; Wirtz M.; Wittkowski D.; Wundheiler B.; Yushkov A.; Zapparrata O.; Zas E.; Zavrtanik D.; Zavrtanik M.; Zehrer L.; Zepeda A.Aab, A.; Abreu, P.; Aglietta, M.; Albury, J. M.; Allekotte, I.; Almela, A.; Alvarez-Muniz, J.; Alves Batista, R.; Anastasi, G. A.; Anchordoqui, L.; Andrada, B.; Andringa, S.; Aramo, C.; Araujo Ferreira, P. R.; Asorey, H.; Assis, P.; Avila, G.; Badescu, A. M.; Bakalova, A.; Balaceanu, A.; Barbato, F.; Barreira Luz, R. J.; Becker, K. H.; Bellido, J. A.; Berat, C.; Bertaina, M. E.; Bertou, X.; Biermann, P. L.; Bister, T.; Biteau, J.; Blazek, J.; Bleve, C.; Bohacova, M.; Boncioli, D.; Bonifazi, C.; Bonneau Arbeletche, L.; Borodai, N.; Botti, A. M.; Brack, J.; Bretz, T.; Briechle, F. L.; Buchholz, P.; Bueno, A.; Buitink, S.; Buscemi, M.; Caballero-Mora, K. S.; Caccianiga, L.; Canfora, F.; Caracas, I.; Carceller, J. M.; Caruso, R.; Castellina, A.; Catalani, F.; Cataldi, G.; Cazon, L.; Cerda, M.; Chinellato, J. A.; Choi, K.; Chudoba, J.; Chytka, L.; Clay, R. W.; Cobos Cerutti, A. C.; Colalillo, R.; Coleman, A.; Coluccia, M. R.; Conceicao, R.; Condorelli, A.; Consolati, G.; Contreras, F.; Convenga, F.; Covault, C. E.; Dasso, S.; Daumiller, K.; Dawson, B. R.; Day, J. A.; de Almeida, R. M.; de Jesus, J.; de Jong, S. J.; de Mauro, G.; de Mello Neto, J. R. T.; de Mitri, I.; de Oliveira, J.; de Oliveira Franco, D.; de Souza, V.; de Vito, E.; Debatin, J.; del Rio, M.; Deligny, O.; Di Matteo, A.; Dobrigkeit, C.; D'Olivo, J. C.; dos Anjos, R. C.; Dova, M. T.; Ebr, J.; Engel, R.; Epicoco, I.; Erdmann, M.; Escobar, C. O.; Etchegoyen, A.; Falcke, H.; Farmer, J.; Farrar, G.; Fauth, A. C.; Fazzini, N.; Feldbusch, F.; Fenu, F.; Fick, B.; Figueira, J. M.; Filipcic, A.; Fodran, T.; Freire, M. M.; Fujii, T.; Fuster, A.; Galea, C.; Galelli, C.; Garcia, B.; Garcia Vegas, A. L.; Gemmeke, H.; Gesualdi, F.; Gherghel-Lascu, A.; Ghia, P. L.; Giaccari, U.; Giammarchi, M.; Giller, M.; Glombitza, J.; Gobbi, F.; Gollan, F.; Golup, G.; Gomez Berisso, M.; Gomez Vitale, P. F.; Gongora, J. P.; Gonzalez, J. M.; Gonzalez, N.; Goos, I.; Gora, D.; Gorgi, A.; Gottowik, M.; Grubb, T. D.; Guarino, F.; Guedes, G. P.; Guido, E.; Hahn, S.; Hampel, M. R.; Hansen, P.; Harari, D.; Harvey, V. M.; Haungs, A.; Hebbeker, T.; Heck, D.; Hill, G. C.; Hojvat, C.; Horandel, J. R.; Horvath, P.; Hrabovsky, M.; Huege, T.; Hulsman, J.; Insolia, A.; Isar, P. G.; Johnsen, J. A.; Jurysek, J.; Kaapa, A.; Kampert, K. H.; Keilhauer, B.; Kemp, J.; Klages, H. O.; Kleifges, M.; Kleinfeller, J.; Kopke, M.; Lago, B. L.; Lang, R. G.; Langner, N.; Leigui de Oliveira, M. A.; Lenok, V.; Letessier-Selvon, A.; Lhenry-Yvon, I.; Lo Presti, D.; Lopes, L.; Lopez, R.; Luce, Q.; Lucero, A.; Lundquist, J. P.; Machado Payeras, A.; Mancarella, G.; Mandat, D.; Manning, B. C.; Manshanden, J.; Mantsch, P.; Marafico, S.; Mariazzi, A. G.; Maris, I. C.; Marsella, G.; Martello, D.; Martinez, H.; Martinez Bravo, O.; Mastrodicasa, M.; Mathes, H. J.; Matthews, J.; Matthiae, G.; Mayotte, E.; Mazur, P. O.; Medina-Tanco, G.; Melo, D.; Menshikov, A.; Merenda, K. -D.; Michal, S.; Micheletti, M. I.; Miramonti, L.; Mollerach, S.; Montanet, F.; Morello, C.; Mostafa, M.; Muller, A. L.; Muller, M. A.; Mulrey, K.; Mussa, R.; Muzio, M.; Namasaka, W. M.; Nellen, L.; Niculescu-Oglinzanu, M.; Niechciol, M.; Nitz, D.; Nosek, D.; Novotny, V.; Nozka, L.; Nucita, A.; Nunez, L. A.; Palatka, M.; Pallotta, J.; Papenbreer, P.; Parente, G.; Parra, A.; Pech, M.; Pedreira, F.; Pekala, J.; Pelayo, R.; Pena-Rodriguez, J.; Perez Armand, J.; Perlin, M.; Perrone, L.; Petrera, S.; Pierog, T.; Pimenta, M.; Pirronello, V.; Platino, M.; Pont, B.; Pothast, M.; Privitera, P.; Prouza, M.; Puyleart, A.; Querchfeld, S.; Rautenberg, J.; Ravignani, D.; Reininghaus, M.; Ridky, J.; Riehn, F.; Risse, M.; Ristori, P.; Rizi, V.; Rodrigues de Carvalho, W.; Rodriguez Rojo, J.; Roncoroni, M. J.; Roth, M.; Roulet, E.; Rovero, A. C.; Ruehl, P.; Saffi, S. J.; Saftoiu, A.; Salamida, F.; Salazar, H.; Salina, G.; Sanabria Gomez, J. D.; Sanchez, F.; Santos, E. M.; Santos, E.; Sarazin, F.; Sarmento, R.; Sarmiento-Cano, C.; Sato, R.; Savina, P.; Schafer, C. M.; Scherini, V.; Schieler, H.; Schimassek, M.; Schimp, M.; Schluter, F.; Schmidt, D.; Scholten, O.; Schovanek, P.; Schroder, F. G.; Schroder, S.; Schulte, J.; Sciutto, S. J.; Scornavacche, M.; Shellard, R. C.; Sigl, G.; Silli, G.; Sima, O.; Smida, R.; Sommers, P.; Soriano, J. F.; Souchard, J.; Squartini, R.; Stadelmaier, M.; Stanca, D.; Stanic, S.; Stasielak, J.; Stassi, P.; Streich, A.; Suarez-Duran, M.; Sudholz, T.; Suomijarvi, T.; Supanitsky, A. D.; Supik, J.; Szadkowski, Z.; Taboada, A.; Tapia, A.; Timmermans, C.; Tkachenko, O.; Tobiska, P.; Todero Peixoto, C. J.; Tome, B.; Travaini, A.; Travnicek, P.; Trimarelli, C.; Trini, M.; Tueros, M.; Ulrich, R.; Unger, M.; Vaclavek, L.; Vacula, M.; Valdes Galicia, J. F.; Valore, L.; Varela, E.; Varma, V. K. C.; Vasquez-Ramirez, A.; Veberic, D.; Ventura, C.; Vergara Quispe, I. D.; Verzi, V.; Vicha, J.; Vink, J.; Vorobiov, S.; Wahlberg, H.; Watson, A. A.; Weber, M.; Weindl, A.; Wiencke, L.; Wilczynski, H.; Winchen, T.; Wirtz, M.; Wittkowski, D.; Wundheiler, B.; Yushkov, A.; Zapparrata, O.; Zas, E.; Zavrtanik, D.; Zavrtanik, M.; Zehrer, L.; Zepeda, A

Demonstrating Agreement between Radio and Fluorescence Measurements of the Depth of Maximum of Extensive Air Showers at the Pierre Auger Observatory

International audienceWe show, for the first time, radio measurements of the depth of shower maximum ($X_\text{max}$) of air showers induced by cosmic rays that are compared to measurements of the established fluorescence method at the same location. Using measurements at the Pierre Auger Observatory we show full compatibility between our radio and the previously published fluorescence data set, and between a subset of air showers observed simultaneously with both radio and fluorescence techniques, a measurement setup unique to the Pierre Auger Observatory. Furthermore, we show radio $X_\text{max}$ resolution as a function of energy and demonstrate the ability to make competitive high-resolution $X_\text{max}$ measurements with even a sparse radio array. With this, we show that the radio technique is capable of cosmic-ray mass composition studies, both at Auger and at other experiments