1. Measurement of the cosmic-ray energy spectrum above 2.5×1018 eV using the Pierre Auger Observatory
- Author
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Jaroslaw Stasielak, Ana Martina Botti, Marcus Niechciol, Alberto Daniel Supanitsky, Alexey Yushkov, Petr Schovánek, Pavel Horváth, Pedro Assis, Nataliia Borodai, Luis Lopes, Luis Nunez, Carla Bleve, Alberto Blanco, Katharine Mulrey, Antonella Castellina, Francesca Zuccarello, Felicia Carla Tiziana Barbato, Emanuele De Vito, Jose Alfredo Bellido Caceres, Fausto Guarino, Jeffrey Brack, Kai Daumiller, Dariusz Gora, Christian Sarmiento-Cano, Alessio Gorgi, Peter Biermann, Teresa Bister, LORENZO CACCIANIGA, Beatriz Garcia, Bruce Dawson, Alena Bakalova, MASSIMO MASTRODICASA, Edivaldo Moura Santos, Stijn Buitink, Bernardo Tomé, Ana Laura Müller, Mario BUSCEMI, Francesco Salamida, Johannes Hulsman, Henryk Wilczyński, Michael Unger, Ronald Cintra Shellard, Miguel Mostafa, Achille Nucita, Frederic Sarazin, Paul Mantsch, Ruben Conceição, Roger Clay, Lukáš Václavek, Giovanni Marsella, Markus Roth, Jakub Jurysek, Lorenzo Cazon, Eva Dos Santos, Corbin Covault, Francesco Fenu, Dalibor Nosek, Rossella Caruso, Alexandra Saftoiu, Tim Huege, Antonio CONDORELLI, Orazio Zapparrata, Jaime Alvarez-Muniz, Denise Boncioli, Guillermo Torralba Elipe, Martin Erdmann, Bruno Lazarotto Lago, Carlos José Todero Peixoto, Geraldina Golup, Jan Pękala, Maximilian Stadelmaier, Raul Sarmento, Enrique Varela, Antoine Letessier selvon, Vincenzo Rizi, Eleonora Guido, Pedro T. Abreu, Rafael Alves Batista, Arjen Van Vliet, and Jan Ebr
- Subjects
Pierre Auger Observatory ,Physics ,Spectral index ,010308 nuclear & particles physics ,Hadron ,Flux ,Cosmic ray ,Astrophysics ,01 natural sciences ,Flattening ,0103 physical sciences ,010306 general physics ,Anisotropy ,Zenith - Abstract
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.
- Published
- 2020