Features of the Energy Spectrum of Cosmic Rays above <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mn>2.5</mml:mn><mml:mo>×</mml:mo><mml:msup><mml:mn>10</mml:mn><mml:mn>18</mml:mn></mml:msup><mml:mtext> </mml:mtext><mml:mtext> </mml:mtext><mml:mi>eV</mml:mi></mml:math> Using the Pierre Auger Observatory
A. Aab, P. Abreu, M. Aglietta, Justin M. Albury, I. Allekotte, A. Almela, M. Castillo, Jaime Álvarez-Muñiz, Rafael Alves Batista, Gioacchino Alex Anastasi, L. Anchordoqui, B. Andrada, S. Andringa, C. Aramo, P. R. Araújo Ferreira, H. Asorey, P. Assis, G. Ávila, Alina Mihaela Badescu, Alena Bakalová, A. Balaceanu, Felicia Barbato, Ricardo Jorge Barreira Luz, K.-H. Becker, Jose A. Bellido, C. Berat, M. E. Bertaina, X. Bertou, Peter L. Biermann, Teresa Bister, Jonathan Biteau, A. Blanco, Jiří Blažek, C. Bleve, M. Boháčová, Denise Boncioli, C. Bonifazi, Luan Bonneau Arbeletche, Nataliia Borodai, Ana Martina Botti, J. Brack, T. Bretz, F. L. Briechle, P. Buchholz, A. Bueno, S. Buitink, Mario Buscemi, K. S. Caballero‐Mora, Lorenzo Caccianiga, L. Calcagni, A. Cancio, Fabrizia Canfora, I. Caracas, J. M. Carceller, R. Caruso, A. Castellina, Fernando Catalani, G. Cataldi, Lorenzo Cazon, M. Cerda, J. A. Chinellato, K. Choi, J. Chudoba, L. Chytka, R. W. Clay, A. C. Cobos Cerutti, R. Colalillo, A. Coleman, M. R. Coluccia, R. Conceição, Antonio Condorelli, Giovanni Consolati, F. Contreras, Fabio Convenga, C. E. Covault, S. Dasso, K. Daumiller, B. R. Dawson, Jarryd A. Day, R. M. de Almeida, J. de Jesús, S. J. de Jong, G. De Mauro, J. R. T. de Mello Neto, I. De Mitri, J. de Oliveira, Danelise de Oliveira Franco, V. de Souza, Emanuele De Vito, J. Debatin, M. del Río, O. Deligny, H.-P. Dembinski, N. Dhital, C. Di Giulio, Armando di Matteo, M. L. Díaz Castro, C. Dobrigkeit, Juan Carlos D’Olivo, Q. Dorosti
Abstract
We report a measurement of the energy spectrum of cosmic rays above 2.5×10$^{18}$ eV based on 215 030 events. New results are presented: at about 1.3×10$^{19}$ eV, the spectral index changes from 2.51±0.03(stat)±0.05(syst) to 3.05±0.05(stat)±0.10(syst), evolving to 5.1±0.3(stat)±0.1(syst) beyond 5×10$^{19}$ eV, while no significant dependence of spectral features on the declination is seen in the accessible range. These features of the spectrum can be reproduced in models with energy-dependent mass composition. The energy density in cosmic rays above 5×10$^{18}$ eV is [5.66±0.03(stat)±1.40(syst)]×10$^{53}$ erg Mpc$^{-3}$.