Inference of the Mass Composition of Cosmic Rays with energies from $\mathbf{10^{18.5}}$ to $\mathbf{10^{20}}$ eV using the Pierre Auger Observatory and Deep Learning
Creators: name: The Pierre Auger Collaboration
name: Halim, A. Abdul
name: Abreu, P.
name: Aglietta, M.
name: Allekotte, I.
name: Cheminant, K. Almeida
name: Almela, A.
name: Aloisio, R.
name: Alvarez-Muñiz, J.
name: Yebra, J. Ammerman
name: Anastasi, G. A.
name: Anchordoqui, L.
name: Andrada, B.
name: Dourado, L. Andrade
name: Andringa, S.
name: Apollonio, L.
name: Aramo, C.
name: Ferreira, P. R. Araújo
name: Arnone, E.
name: Velázquez, J. C. Arteaga
name: Assis, P.
name: Avila, G.
name: Avocone, E.
name: Bakalova, A.
name: Barbato, F.
name: Mocellin, A. Bartz
name: Berat, C.
name: Bertaina, M. E.
name: Bhatta, G.
name: Bianciotto, M.
name: Biermann, P. L.
name: Binet, V.
name: Bismark, K.
name: Bister, T.
name: Biteau, J.
name: Blazek, J.
name: Bleve, C.
name: Blümer, J.
name: Boháčová, M.
name: Boncioli, D.
name: Bonifazi, C.
name: Arbeletche, L. Bonneau
name: Borodai, N.
name: Brack, J.
name: Orchera, P. G. Brichetto
name: Briechle, F. L.
name: Bueno, A.
name: Buitink, S.
name: Buscemi, M.
name: Büsken, M.
name: Bwembya, A.
name: Caballero-Mora, K. S.
name: Cabana-Freire, S.
name: Caccianiga, L.
name: Campuzano, F.
name: Caruso, R.
name: Castellina, A.
name: Catalani, F.
name: Cataldi, G.
name: Cazon, L.
name: Cerda, M.
name: Čermáková, B.
name: Cermenati, A.
name: Chinellato, J. A.
name: Chudoba, J.
name: Chytka, L.
name: Clay, R. W.
name: Cerutti, A. C. Cobos
name: Colalillo, R.
name: Coluccia, M. R.
name: Conceição, R.
name: Condorelli, A.
name: Consolati, G.
name: Conte, M.
name: Convenga, F.
name: Santos, D. Correia dos
name: Costa, P. J.
name: Covault, C. E.
name: Cristinziani, M.
name: Sanchez, C. S. Cruz
name: Dasso, S.
name: Daumiller, K.
name: Dawson, B. R.
name: de Almeida, R. M.
name: de Errico, B.
name: de Jesús, J.
name: de Jong, S. J.
name: Neto, J. R. T. de Mello
name: De Mitri, I.
name: de Oliveira, J.
name: Franco, D. de Oliveira
name: de Palma, F.
name: de Souza, V.
name: De Vito, E.
name: Del Popolo, A.
name: Deligny, O.
name: Denner, N.
name: Deval, L.
name: di Matteo, A.
name: do, J. A.
name: Dobre, M.
name: Dobrigkeit, C.
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name: Mendes, L. M. Domingues
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name: Anjos, J. C. dos
name: Anjos, R. C. dos
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name: Engel, R.
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name: Erdmann, M.
name: Etchegoyen, A.
name: Evoli, C.
name: Falcke, H.
name: Farrar, G.
name: Fauth, A. C.
name: Fehler, T.
name: Feldbusch, F.
name: Fenu, F.
name: Fernandes, A.
name: Fick, B.
name: Figueira, J. M.
name: Filip, P.
name: Filipčič, A.
name: Fitoussi, T.
name: Flaggs, B.
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name: Galea, C.
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name: Gherghel-Lascu, A.
name: Ghia, P. L.
name: Giaccari, U.
name: Glombitza, J.
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name: Huege, T.
name: Insolia, A.
name: Isar, P. G.
name: Janecek, P.
name: Jilek, V.
name: Johnsen, J. A.
name: Jurysek, J.
name: Kampert, K. -H.
name: Keilhauer, B.
name: Khakurdikar, A.
name: Covilakam, V. V. Kizakke
name: Klages, H. O.
name: Kleifges, M.
name: Knapp, F.
name: Köhler, J.
name: Krieger, F.
name: Kunka, N.
name: Lago, B. L.
name: Langner, N.
name: de Oliveira, M. A. Leigui
name: Lema-Capeans, Y.
name: Letessier-Selvon, A.
name: Lhenry-Yvon, I.
name: Lopes, L.
name: Lu, L.
name: Luce, Q.
name: Lundquist, J. P.
name: Payeras, A. Machado
name: Majercakova, M.
name: Mandat, D.
name: Manning, B. C.
name: Mantsch, P.
name: Mariani, F. M.
name: Mariazzi, A. G.
name: Mariş, I. C.
name: Marsella, G.
name: Martello, D.
name: Martinelli, S.
name: Bravo, O. Martínez
name: Martins, M. A.
name: Mathes, H. -J.
name: Matthews, J.
name: Matthiae, G.
name: Mayotte, E.
name: Mayotte, S.
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name: Mulrey, K.
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name: Nitz, D.
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name: Oliveira, C.
name: Palatka, M.
name: Pallotta, J.
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name: Parente, G.
name: Paulsen, T.
name: Pawlowsky, J.
name: Pech, M.
name: Pękala, J.
name: Pelayo, R.
name: Pelgrims, V.
name: Pereira, L. A. S.
name: Martins, E. E. Pereira
name: Bertolli, C. Pérez
name: Perrone, L.
name: Petrera, S.
name: Petrucci, C.
name: Pierog, T.
name: Pimenta, M.
name: Platino, M.
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name: Shahvar, M. Pourmohammad
name: Privitera, P.
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name: Ravignani, D.
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name: Risse, M.
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name: de Carvalho, W. Rodrigues
name: Rodriguez, E.
name: Rojo, J. Rodriguez
name: Roncoroni, M. J.
name: Rossoni, S.
name: Roth, M.
name: Roulet, E.
name: Rovero, A. C.
name: Saftoiu, A.
name: Saharan, M.
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name: Schmidt, D.
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name: Schulz, T.
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name: Scornavacche, M.
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name: Supanitsky, A. D.
name: Svozilikova, Z.
name: Szadkowski, Z.
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name: Tapia, A.
name: Taricco, C.
name: Timmermans, C.
name: Tkachenko, O.
name: Tobiska, P.
name: Peixoto, C. J. Todero
name: Tomé, B.
name: Torrès, Z.
name: Travaini, A.
name: Travnicek, P.
name: Tueros, M.
name: Unger, M.
name: Uzeiroska, R.
name: Vaclavek, L.
name: Vacula, M.
name: Galicia, J. F. Valdés
name: Valore, L.
name: Varela, E.
name: Vašíčková, V.
name: Vásquez-Ramírez, A.
name: Veberič, D.
name: Quispe, I. D. Vergara
name: Verzi, V.
name: Vicha, J.
name: Vink, J.
name: Vorobiov, S.
name: Watanabe, C.
name: Watson, A. A.
name: Weindl, A.
name: Wiencke, L.
name: Wilczyński, H.
name: Wittkowski, D.
name: Wundheiler, B.
name: Yue, B.
name: Yushkov, A.
name: Zapparrata, O.
name: Zas, E.
name: Zavrtanik, D.
name: Zavrtanik, M.
Publisher: name: arXiv
Year: 2024
Subjects: subject: High Energy Astrophysical Phenomena (astro-ph.HE)
subject: Instrumentation and Methods for Astrophysics (astro-ph.IM)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: We present measurements of the atmospheric depth of the shower maximum $X_\mathrm{max}$, inferred for the first time on an event-by-event level using the Surface Detector of the Pierre Auger Observatory. Using deep learning, we were able to extend measurements of the $X_\mathrm{max}$ distributions up to energies of 100 EeV ($10^{20}$ eV), not yet revealed by current measurements, providing new insights into the mass composition of cosmic rays at extreme energies. Gaining a 10-fold increase in statistics compared to the Fluorescence Detector data, we find evidence that the rate of change of the average $X_\mathrm{max}$ with the logarithm of energy features three breaks at $6.5\pm0.6~(\mathrm{stat})\pm1~(\mathrm{sys})$ EeV, $11\pm 2~(\mathrm{stat})\pm1~(\mathrm{sys})$ EeV, and $31\pm5~(\mathrm{stat})\pm3~(\mathrm{sys})$ EeV, in the vicinity to the three prominent features (ankle, instep, suppression) of the cosmic-ray flux. The energy evolution of the mean and standard deviation of the measured $X_\mathrm{max}$ distributions indicates that the mass composition becomes increasingly heavier and purer, thus being incompatible with a large fraction of light nuclei between 50 EeV and 100 EeV.
description: Version accepted for publication in Phys. Rev. Lett., 9 pages, 3 figures, 1 table