The energy spectrum of cosmic rays beyond the turn-down around $$\varvec{10^{17}}$$ eV as measured with the surface detector of the Pierre Auger Observatory
P. Abreu, M. Aglietta, Justin M. Albury, I. Allekotte, A. Almela, Jaime Álvarez-Muñiz, Rafael Alves Batista, Gioacchino Alex Anastasi, L. Anchordoqui, B. Andrada, S. Andringa, C. Aramo, Paulo Ricardo Araújo Ferreira, J. C. Arteaga Velázquez, H. Asorey, P. Assis, Gualberto Avila, Alina Mihaela Badescu, Alena Bakalová, A. Balaceanu, Felicia Barbato, Ricardo Jorge Barreira Luz, K. Becker, Jose A. Bellido, C. Bérat, М. Бертаина, X. Bertou, Peter L. Biermann, P. Billoir, Virginia Binet, K. Bismark, Teresa Bister, J. Biteau, Jiří Blažek, C. Bleve, M. Boháčová, Denise Boncioli, C. Bonifazi, L. Bonneau Arbeletche, Nataliia Borodai, Ana Martina Botti, J. Brack, T. Bretz, P. G. Brichetto Orchera, F. L. Briechle, P. Buchholz, A. Bueno, S. Buitink, Mario Buscemi, M. Büsken, K. S. Caballero‐Mora, Lorenzo Caccianiga, Fabrizia Canfora, I. Caracas, Juan Miguel Carceller, R. Caruso, A. Castellina, F. Catalani, G. Cataldi, Lorenzo Cazon, M. Cerda, J. A. Chinellato, J. Chudoba, L. Chytka, R. W. Clay, A. C. Cobos Cerutti, R. Colalillo, Alan Coleman, M. R. Coluccia, R. Conceição, Antonio Condorelli, Giovanni Consolati, F. Contreras, Fabio Convenga, Diego Correia dos Santos, C. E. Covault, S. Dasso, K. Daumiller, B. R. Dawson, J.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, F. de Palma, V. de Souza, Emanuele De Vito, M. del Río, O. Deligny, Armando di Matteo, C. Dobrigkeit, J. C. D’Olivo, Luis Miguel Domingues Mendes, R. C. dos Anjos, D. dos Santos, M.T. Dova
Abstract
Abstract 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.