Measurement of the cosmic-ray energy spectrum above $2.5{\times} 10^{18}$ eV using the Pierre Auger Observatory

Alexander Aab , Pedro Abreu , Marco Aglietta , Justin M Albury , Ingomar Allekotte , Alejandro Almela , Jesus Alvarez Castillo , Jaime Alvarez-Muñiz , Rafael Alves Batista , Gioacchino Alex Anastasi , Luis Anchordoqui , Belén Andrada , Sofia Andringa , Carla Aramo , Paulo Ricardo Araújo Ferreira , Hernán Gonzalo Asorey , Pedro Assis , Gualberto Avila , Alina Mihaela Badescu , Alena Bakalova , Alexandru Balaceanu , Felicia Barbato , Ricardo Jorge Barreira Luz , Karl-Heinz Becker , Jose A Bellido , Corinne Berat (1) , Mario Edoardo Bertaina , Xavier Bertou , Peter Biermann , Terasa Bister , Jonathan Biteau (2) , Alberto Blanco , Jiri Blazek , Carla Bleve (1) , Martina Boháčová , Denise Boncioli , Carla Bonifazi , Luan Bonneau Arbeletche , Nataliia Borodai , Ana Martina Botti , Jeffrey Brack , Thomas Bretz , Florian Lukas Briechle , Peter Buchholz , Antonio Bueno , Stijn Buitink , Mario Buscemi , Karen S Caballero-Mora , Lorenzo Caccianiga , Laura Calcagni , Ángel Cancio , Fabrizia Canfora , Ioana Caracas , Juan Miguel Carceller , Rossella Caruso , Antonella Castellina , Fernando Catalani , Gabriella Cataldi , Lorenzo Cazon , Marcos Cerda , Jose Augusto Chinellato , Koun Choi , Jiri Chudoba , Ladislav Chytka , Roger W Clay , Agustín Cobos Cerutti , Roberta Colalillo , Alan Coleman , Maria Rita Coluccia , Ruben Conceição , Antonio Condorelli , Giovanni Consolati , Fernando Contreras , Fabio Convenga , Corbin Covault , Sergio Dasso , Kai Daumiller , Bruce R Dawson , Jarryd A Day , Rogerio M de Almeida , Joaquín de Jesús , Sijbrand J de Jong , Giuseppe de Mauro , Joao de Mello Neto , Ivan de Mitri , Jaime de Oliveira , Danelise de Oliveira Franco , Vitor de Souza , Emanuele de Vito , Joachim Debatin , Mariano del Río , Olivier Deligny (2) , Hans Dembinski , Niraj Dhital , Claudio Di Giulio , Armando Di Matteo , Mary Lucia Díaz Castro , Carola Dobrigkeit , Juan Carlos d'Olivo , Qader Dorosti , Rita dos Anjos , Maria Teresa Dova , Jan Ebr , Ralph Engel , Italo Epicoco , Martin Erdmann , Carlos O Escobar , Alberto Etchegoyen , Heino Falcke , John Farmer , Glennys Farrar , Anderson Fauth , Norberto Fazzini , Fridtjof Feldbusch , Francesco Fenu , Brian Fick , Juan Manuel Figueira , Andrej Filipčič , Tomas Fodran , Martín Miguel Freire , Toshihiro Fujii , Alan Fuster , Cristina Galea , Claudio Galelli , Beatriz García , Adrianna Luz Garcia Vegas , Hartmut Gemmeke , Flavia Gesualdi , Alexandru Gherghel-Lascu , Piera Luisa Ghia (2) , Ugo Giaccari , Marco Giammarchi , Maria Giller , Jonas Glombitza , Fabian Gobbi , Fernando Gollan , Geraldina Golup , Mariano Gómez Berisso , Primo F Gómez Vitale , Juan Pablo Gongora , Nicolás González , Isabel Goos , Dariusz Góra , Alessio Gorgi , Marvin Gottowik , Trent D Grubb , Fausto Guarino , Germano Guedes , Eleonora Guido , Steffen Hahn , Robert Halliday , Matías Rolf Hampel , Patricia Hansen , Diego Harari , Violet M Harvey , Andreas Haungs , Thomas Hebbeker , Dieter Heck , Gary C Hill , Carlos Hojvat , Jörg Hörandel , Pavel Horvath , Miroslav Hrabovský , Tim Huege , Johannes Hulsman , Antonio Insolia , Paula Gina Isar , Jeffrey A Johnsen , Jakub Jurysek , Alex Kääpä , Karl-Heinz Kampert , Bianca Keilhauer , Julian Kemp , Hans Klages , Matthias Kleifges , Jonny Kleinfeller , Marcel Köpke , Gasper Kukec Mezek , Bruno L Lago , Danielle Lahurd , Rodrigo Guedes Lang , Marcelo Augusto Leigui de Oliveira , Vladimir Lenok , Antoine Letessier-Selvon (3) , Isabelle Lhenry-Yvon (2) , Domenico Lo Presti , Luis Lopes , Rebeca López , Ryan Lorek , Quentin Luce , Agustin Lucero , Allan Machado Payeras , Max Malacari , Giovanni Mancarella , Dusan Mandat , Bradley C Manning , Julien Manshanden , Paul Mantsch , Sullivan Marafico (2) , Analisa Mariazzi , Ioana Mariş , Giovanni Marsella , Daniele Martello , Humberto Martinez , Oscar Martínez Bravo , Massimo Mastrodicasa , Hermann-Josef Mathes , James Matthews , Giorgio Matthiae , Eric Mayotte , Peter Mazur , Gustavo Medina-Tanco , Diego Melo , Alexander Menshikov , Kevin-Druis Merenda , Stanislav Michal , Maria Isabel Micheletti , Lino Miramonti , Daniela Mockler , Silvia Mollerach , François Montanet (1) , Carlo Morello , Miguel Mostafá , Ana L Müller , Marcio Aparecido Muller , Katharine Mulrey , Roberto Mussa , Marco Muzio , Wilson M Namasaka , Lukas Nellen , Phong H Nguyen , Mihai Niculescu-Oglinzanu , Marcus Niechciol , Dave Nitz , Dalibor Nosek , Vladimir Novotny , Libor Nožka , Achille Nucita , Luis Núñez , Miroslav Palatka , Juan Pallotta , Maria Paola Panetta , Philipp Papenbreer , Gonzalo Parente , Alejandra Parra , Miroslav Pech , Francisco Pedreira , Jan Pękala , Rodrigo Pelayo , Jesús Peña-Rodriguez , Johnnier Perez Armand , Matías Perlin , Lorenzo Perrone , Christine Peters , Sergio Petrera , Tanguy Pierog , Mário Pimenta , Valerio Pirronello , Manuel Platino , Bjarni Pont , Mart Pothast , Paolo Privitera , Michael Prouza , Andrew Puyleart , Sven Querchfeld , Julian Rautenberg , Diego Ravignani , Maximilian Reininghaus , Jan Ridky , Felix Riehn , Markus Risse , Pablo Ristori , Vincenzo Rizi , Washington Rodrigues de Carvalho , Gonzalo Rodriguez Fernandez , Jorge Rubén Rodriguez Rojo , Matías J Roncoroni , Markus Roth , Esteban Roulet , Adrian Rovero , Philip Ruehl , Steven J Saffi , Alexandra Saftoiu , Francesco Salamida , Humberto Salazar , Gaetano Salina , Jose Sanabria Gomez , Federico Sánchez , Edivaldo Moura Santos , Eva Santos , Fred Sarazin , Raul Sarmento , Christian Sarmiento-Cano , Ricardo Sato , Pierpaolo Savina (2) , Christoph Schäfer , Viviana Scherini , Harald Schieler , Martin Schimassek , Michael Schimp , Felix Schlüter , David Schmidt , Olaf Scholten , Petr Schovánek , Frank G Schröder , Sonja Schröder , Alexander Schulz , Sergio Sciutto , Marina Scornavacche , Ronald C Shellard , Guenter Sigl , Gaia Silli , Octavian Sima , Radomir Šmída , Paul Sommers , Jorge F Soriano , Julien Souchard (1) , Ruben Squartini , Maximilian Stadelmaier , Denis Stanca , Samo Stanič , Jaroslaw Stasielak , Patrick Stassi (1) , Alexander Streich , Mauricio Suárez-Durán , Tristan Sudholz , Tiina Suomijärvi (2) , a Daniel Supanitsky , Jan Šupík , Zbigniew Szadkowski , Alvaro Taboada , Alex Tapia , Charles Timmermans , Olena Tkachenko , Petr Tobiska , Carlos J Todero Peixoto , Bernardo Tomé , Guillermo Torralba Elipe , Andres Travaini , Petr Travnicek , Caterina Trimarelli , Marta Trini , Matias Tueros , Ralf Ulrich , Michael Unger , Martin Urban , Lukáš Vaclavek , Martin Vacula , Jose F Valdés Galicia , Ines Valiño , Laura Valore , Arjen van Vliet , Enrique Varela , Bernardo Vargas Cárdenas , Adriana Vásquez-Ramírez , Darko Veberič , Cynthia Ventura , Indira D Vergara Quispe , Valerio Verzi , Jakub Vicha , Luis Villaseñor , Jacco Vink , Serguei Vorobiov , Hernan Wahlberg , Alan Watson , Marc Weber , Andreas Weindl , Lawrence Wiencke , Henryk Wilczyński , Tobias Winchen , Marcus Wirtz , David Wittkowski , Brian Wundheiler , Alexey Yushkov , Orazio Zapparrata , Enrique Zas , Danilo Zavrtanik , Marko Zavrtanik , Lukas Zehrer , Arnulfo Zepeda , Michael Ziolkowski , Francesca Zuccarello

1 LPSC - Laboratoire de Physique Subatomique et de Cosmologie
2 IJCLab - Laboratoire de Physique des 2 Infinis Irène Joliot-Curie
3 LPNHE (UMR_7585) - Laboratoire de Physique Nucléaire et de Hautes Énergies

We report a measurement of the energy spectrum of cosmic rays for energies above 2.5×1018  eV based on 215,030 events recorded with zenith angles below 60°. A key feature of the work is that the estimates of the energies are independent of assumptions about the unknown hadronic physics or of the primary mass composition. The measurement is the most precise made hitherto with the accumulated exposure being so large that the measurements of the flux are dominated by systematic uncertainties except at energies above 5×1019  eV. The principal conclusions are(1) The flattening of the spectrum near 5×1018  eV, the so-called “ankle,” is confirmed.(2) The steepening of the spectrum at around 5×1019  eV is confirmed.(3) A new feature has been identified in the spectrum: in the region above the ankle the spectral index γ of the particle flux (∝E-γ) changes from 2.51±0.03 (stat)±0.05 (syst) to 3.05±0.05 (stat)±0.10 (syst) before changing sharply to 5.1±0.3 (stat)±0.1 (syst) above 5×1019  eV.(4) No evidence for any dependence of the spectrum on declination has been found other than a mild excess from the Southern Hemisphere that is consistent with the anisotropy observed above 8×1018  eV.

Mots clés: Experiments in gravity; cosmology; cosmic rays; cosmic radiation: energy spectrum; flux; power spectrum; mass spectrum; UHE; observatory; anisotropy; Auger

Domaines: Astrophysique [astro-ph]

Alexander Aab, Pedro Abreu, Marco Aglietta, Justin M Albury, Ingomar Allekotte, et al.. Measurement of the cosmic-ray energy spectrum above $2.5{\times} 10^{18}$ eV using the Pierre Auger Observatory. Physical Review D, 2020, 102 (6), pp.062005. ⟨10.1103/PhysRevD.102.062005⟩. ⟨hal-02933950⟩