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

• Main Authors: Abreu, P, Almela, A, Alvarez-Muñiz, J, Aramo, C, Ferreira, P. R. Araújo, Avila, G, Balaceanu, A, Becker, K. H, Bertou, X, Biermann, P. L, Bonifazi, C, Brack, J, Buchholz, P, Calcagni, L, Canfora, F, Caruso, R, Choi, K, Clay, R. W, Conceição, R, Consolati, G, Convenga, F, Covault, C. E, Dasso, S, Dawson, B. R, De Mauro, G, De Vito, E, D'Olivo, J. C, Dova, M. T, Ebr, J, Farmer, J, Fauth, A. C, Fazzini, N, Feldbusch, F, Fick, B, Figueira, J. M, Freire, M. M, Fujii, T, Gherghel-Lascu, A, Glombitza, J, Golup, G, Góra, D, Guarino, F, Hahn, S, Hojvat, C, Isar, P. G, Kampert, K. H, Kemp, J, Lenok, V, Lopes, L, López, R, Lucero, A, Payeras, A. Machado, Malacari, M, Manning, B. C, Mantsch, P, Marafico, S, Matthews, J, Melo, D, Mockler, D, Mollerach, S, Montanet, F, Nellen, L, Niculescu-Oglinzanu, M, Niechciol, M, Novotny, V, Núñez, L. A, Parra, A, Perlin, M, Peters, C, Pierog, T, Platino, M, Pothast, M, Rautenberg, J, Reininghaus, M, Ristori, P, de Carvalho, W. Rodrigues, Fernandez, G. Rodriguez, Rojo, J. Rodriguez, Saftoiu, A, Salamida, F, Gomez, J. D. Sanabria, Sarazin, F, Sarmento, R, Sarmiento-Cano, C, Sato, R, Schäfer, C, Scherini, V, Schimp, M, Schröder, S, Shellard, R. C, Sigl, G, Sommers, P, Tueros, M, Unger, M, Galicia, J. F. Valdés, Vink, J, Wilczyński, H, Winchen, T, Wittkowski, D, Zavrtanik, D
• Format: Journal Article
• Language: English
• Published: 14-08-2020
• Subjects: Physics - High Energy Astrophysical Phenomena
• DOI: 10.48550/arxiv.2008.06488

Phys. Rev. Lett. 125, 121106 (2020) We report a measurement of the energy spectrum of cosmic rays above
$2.5{\times} 10^{18}$ eV based on $215,030$ events. New results are presented:
at about $1.3{\times} 10^{19}$ eV, the spectral index changes from $2.51 \pm
0.03 \textrm{ (stat.)} \pm 0.05 \textrm{ (sys.)}$ to $3.05 \pm 0.05 \textrm{
(stat.)}\pm 0.10\textrm{ (sys.)}$, evolving to $5.1\pm0.3\textrm{ (stat.)} \pm
0.1\textrm{ (sys.)}$ beyond $5{\times} 10^{19}$ 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
$5{\times} 10^{18}$ eV is $(5.66 \pm 0.03 \textrm{ (stat.)} \pm 1.40 \textrm{
(sys.)} ) {\times} 10^{53}~$erg Mpc$^{-3}$.