Work

Depth of maximum of air-shower profiles above 10 17.7 eV measured with the fluorescence detector of the Pierre Auger Observatory

Year: 2026

Type: article

Abstract: We present measurements of the depth of shower maximum, X$_{max}$, for cosmic-ray-induced extensive air showers recorded by the fluorescence detector of the Pierre Auger Observatory over 17 years. The dataset covers primary energies from 10$^{17.7}$ eV to beyond 10$^{19.6}$eV. With improved event reconstruction and an exposure 2.4 times larger than in our previous analysis, this work confirms and refines our conclusions on the mass composition at ultrahigh energies. The energy evolution of the mean X$_{max}$ exhibits a pronounced break at a cosmic-ray energy of about 10$^{18.4}$ eV, providing direct, model-independent evidence for a change in the evolution of the mass composition. Independently, the observed decrease of the X$_{max}$ fluctuations with energy indicates a transition toward a heavier and less diverse primary mass composition. No statistically significant declination dependence of the X$_{max}$ distributions is observed within the exposure of the Observatory, consistent with an isotropic mass composition at the sensitivity of this analysis. The mean and standard deviation of the X$_{max}$ distributions, interpreted with air-shower simulations, yield the energy dependence of the average and variance of the logarithmic mass of cosmic rays arriving at Earth. Furthermore, energy-dependent fractional abundances of four representative primary-mass groups (p, He, CNO, Fe) are obtained by fitting the observed X$_{max}$ distributions in each energy bin with a weighted sum of elemental templates. These results provide strong evidence against a long-standing assumption that ultrahigh-energy cosmic rays are predominantly protons: above 1018.4 eV, the average cosmic-ray mass increases, accompanied by a steadily decreasing diversity in the elemental composition.

Source: Repository KITopen (Karlsruhe Institute of Technology)

DOI: 10.5445/ir/1000196631

Authors: Pierre Auger Collaboration, Abdul Halim, A., Abreu, P., Aglietta, M., Ahmed, Mulan, Allekotte, I., Almeida Cheminant, K., Aloisio, R., Alvarez-Muñiz, J., Ambrosone, A., Ammerman Yebra, J., Anchordoqui, L., Andrada, B., Andrade Dourado, L., Apollonio, L., Aramo, C., Arnone, E., Arteaga Velázquez, Juan Carlos, Assis, P., Avila, G., Avocone, E., Bakalova, A., Balibrea, Yosel, Baluta, Anastasia, Barbato, F., Bartz Mocellin, A., Behler, Juan Pablo, Bellido, J. A., Berat, C., Bertaina, M. E., Bianciotto, M., Biermann, P. L., Binet, V., Bismark, K., Bister, T., Biteau, J., Blazek, J., Blümer, J., Boháčová, Martina, Boncioli, D., Bonifazi, C., Borodai, N., Brack, J., Brichetto Orquera, P. Gabriel, Bueno, A., Buitink, S., Bwembya, A., Caba Pineda, Thara Rubi, Caballero-Mora, K. S., Cabana-Freire, S., Caccianiga, L., Caraça-Valente, J., Caruso, R., Castellina, A., Catalani, F., Cataldi, G., Cazon, L., Cerda, M., Čermáková, B., Cermenati, A., Cerny, Karel, Chinellato, J. A., Chudoba, J., Chytka, L., Clay, R. W., Cobos Cerutti, A. C., Colalillo, R., Conceição, R., Consolati, G., Conte, M., Convenga, F., Correia dos Santos, D., Costa, P. J., Covault, C. E., Cristinziani, M., Cruz Sanchez, C. S., Dasso, S., Daumiller, K., Dawson, B. R., de Almeida, R. M., de Boone, E.-T., de Errico, B., de Jesús, J., de Jong, S. J., de Mello Neto, J. R. T., De Mitri, I., de Oliveira Franco, D., de Palma, F., de Souza, V., De Vito, E., Del Popolo, A., Deligny, O., Denner, N., Denner Syrokvas, Karolina, Deval, L., di Matteo, A., Dobrigkeit, C., d'Olivo, Juan Carlos, Domingues Mendes, L. M., Dominguez, Tomás, Dominguez Ballesteros, Yessica, Dorosti, Q., dos Anjos, R. C., Ebr, J., Ellwanger, F., Engel, R., Epicoco, I., Erdmann, M., Etchegoyen, A., Evoli, C., Falcke, H., Farrar, G., Fauth, A. C., Fehler, T., Feldbusch, F., Fernandes, A., Fernández Alonso, Mateo, Fick, B., Figueira, J. M., Filip, P., Filipčič, Andrej, Fitoussi, T., Flaggs, B., Franco, A., Freitas, M., Fujii, T., Fuster, A., Galea, C., García, B., Gaudu, C., Ghia, P. L., Giaccari, U., Giammarco, Matteo, Glaser, C., Gobbi, F., Gollan, F., Golup, G., Gómez Vitale, P. F., Gongora, J. P., González, N., Góra, D., Gorgi, A., Gottowik, M., Guarino, F., Guedes, G. P., Guerra, Yan Carlos, Gülzow, L., Hahn, S., Hamal, P., Hampel, M. R., Hansen, Patricia, Harvey, V. M., Haungs, A., Havelka, Matej, Hebbeker, T., Hojvat, C., Hörandel, J. R., Horvath, P., Hrabovský, Miroslav, Huege, T., Insolia, A., Isar, P. G., Ismaiel, M., Janecek, P., Jilek, V., Kampert, K.-H., Keilhauer, B., Kizakke Covilakam, V. V., Klages, H. O., Kleifges, M., Klingel, Alina, Köhler, J., Krieger, F., Kubatova, M., Kunka, N., Lago, B. L., Langner, N., Leal, N., Leigui de Oliveira, M. A., Lema-Capeans, Y., Letessier-Selvon, A., Lhenry-Yvon, I., Lopes, L., Lundquist, J. P., Mallamaci, M., Mancuso, Salvatore, Mandat, D., Mantsch, P., Mariazzi, A. G., Marinelli, Costanza, Mariş, I. C., Marsella, G., Martello, D., Martinelli, S., Martínez Bravo, O., Martínez-Mendez, Alexander, Martins, M. A., Mathes, H.-J., Matthews, J., Matthiae, G., Mayotte, E., Mayotte, S., Mazur, P. O., Medina-Tanco, G., Meinert, J., Melo, D., Menshikov, A., Merx, C., Michal, S., Micheletti, M. I., Miramonti, L., Mogarkar, M., Mollerach, S., Montanet, F., Morejon, L., Mulrey, K., Mussa, R., Namasaka, W. M., Negi, S., Nellen, L., Nguyen, K., Nicora, G., Niechciol, M., Nitz, D., Nosek, D., Novikov, A., Novotny, Vladimir, Nožka, Libor, Nucita, A., Núñez, L. A., Nuza, Sebastián E., Ochoa, J., Olegario, Marcos, Oliveira, C., Östman, L., Palatka, M., Pallotta, J., Parente, G., Paulsen, T., Pawlowsky, J., Pech, M., Pȩkala, J., Pelayo, R., Pelgrims, V., Pérez Bertolli, C., Perrone, L., Petrera, S., Pierog, T., Pimenta, M., Platino, M., Pont, B., Pourmohammad Shahvar, M., Privitera, P., Priyadarshi, C., Prouza, M., Pytel, K., Querchfeld, S., Rautenberg, J., Ravignani, D., Reginatto Akim, J. V., Rennó, Mateus Zeferino, Reuzki, A., Ridky, J., Riehn, F., Risse, M., Rizi, V., Rocha Moldes, Brais, Rodriguez, E., Rodriguez Fernandez, G., Rodriguez Rojo, J., Rossoni, S., Roth, M., Roulet, E., Rovero, A. C., Saftoiu, A., Saharan, M., Salamida, F., Salazar, Humberto, Salina, G., Sampathkumar, P., San Martin, N., Sanabria Gomez, J. D., Sánchez, F., Sánchez Rodriguez, Francisco M., Santos, E., Sarazin, F., Sarmento, R., Sato, R., Savina, P., Scherini, V., Schieler, H., Schimp, M., Schmidt, D., Scholten, O., Schoorlemmer, H., Schovánek, Petr, Schröder, F. G., Schulte, J., Schulz, T., Sciutto, S. J., Scornavacche, M., Sedoski, A., Sehgal, S., Shivashankara, S. U., Sigl, G., Simkova, Katarina, Simon, F., Šmída, Radomir, Soares Sippert, Sarah, Sommers, P., Stanič, S., Stasielak, J., Stassi, P., Strähnz, S., Straub, M., Suomijärvi, Tiina, Supanitsky, A. D., Svozilikova, Z., Szadkowski, Z., Tairli, F., Tapia, A., Taricco, C., Timmermans, C., Tkachenko, O., Tobiska, P., Todero Peixoto, C. J., Tomé, B., Travaini, A., Travnicek, P., Trimarelli, C., Tueros, M., Unger, M., Uzeiroska-Geyik, Rukije, Vaclavek, L., Vacula, M., Vaiman, I., Valdés Galicia, J. F., Valore, L., van Dillen, P., Varela, E., Vašíčková, V., Vásquez-Ramírez, A., Veberič, D., Vergara Quispe, I. D., Verpoest, S., Verzi, V., Vicha, J., Vorobiov, S., Vuta, J. B., Watanabe, C., Watson, A. A., Weindl, A., Weitz, M., Wiencke, L., Wilczyński, H., Wundheiler, B., Yue, B., Yushkov, A., Zas, E., Zavrtanik, D., Zavrtanik, M.

Language: English

Topic: Astrophysics and Cosmic Phenomena

Subfield: Nuclear and High Energy Physics

Field: Physics and Astronomy

Domain: Physical Sciences

Open Access status: green

Funders: National Science Foundation, U.S. Department of Energy, Grainger Foundation, Strong, Ministerio de Ciencia, Innovación y Universidades, European Commission, Deutsche Forschungsgemeinschaft, Ministerstvo Školství, Mládeže a Tělovýchovy, Grantová Agentura České Republiky, Fonds De La Recherche Scientifique - FNRS, Consejo Nacional de Investigaciones Científicas y Técnicas, Fonds Wetenschappelijk Onderzoek, Consejo Nacional de Ciencia y Tecnología, Nederlandse Organisatie voor Wetenschappelijk Onderzoek, Ministério da Ciência, Tecnologia e Inovação, Centre National de la Recherche Scientifique, Istituto Nazionale di Astrofisica, Universidad Nacional Autónoma de México, Benemérita Universidad Autónoma de Puebla, Xunta de Galicia, Vlaamse regering, Istituto Nazionale di Fisica Nucleare, Ministerium für Kultur und Wissenschaft des Landes Nordrhein-Westfalen, Helmholtz Alliance for Astroparticle Physics, Ministero dell'Università e della Ricerca, Fundação para a Ciência e a Tecnologia, Agencia Nacional de Promoción Científica y Tecnológica, European Regional Development Fund, Agencia Estatal de Investigación, Institut National de Physique Nucléaire et de Physique des Particules

Awards: G1086978037, G1105844351, Pierre Auger Project, G1151900320, G1167214205, G1175115578, G12500569, G1404832668, G1496055848, G1578237752, G1603472241, G1610934229, G1727275246, G176604203, G1840991089, G1935710221, G222768804, G2230854319, G2233490251, G2262748287, G2366462802, G2601397997, G2677629327, G2678520069, G291036901, G300979063, G3219270595, G3286760496, G3295960771, G3405914644, G3480869486, G3486424601, G3490171961, G3523651922, G3622461675, G3681454997, G3694284866, G3700295401, G3735356012, G3755077010, G3810236772, G3886017652, G3999575733, G4042783231, G4080017644, G410571670, G4131035492, Race in the Histories of Science and Medicine: A Review Essay and a Research Agenda, G4212894969, G425668148, G4280972364, G4320224000, G4396925471, G4462967385, G4507218474, G451917667, G4529325604, G491712853, G5080475149, G5100556825, G517294234, G523076202, G5356239126, G5385376234, Evaluation of the specificity and early diagnostic value of novel peptide biomarkers of Type 1 Diabetes, G5616713406, G5635532810, G5641063287, G584027024, G585908603, G5860975833, G589433610, G5916014575, G593054264, G5967599077, G6010476436, G6230683201, G6261681677, Pierre Auger Observatory - participation of the Czech Republic, Astrophysics Center for Multimessenger studies in Europe, G6494969456, G6753605191, G6761430300, G6869766708, G6958583472, G7502932367, G7517989378, STUDIES OF HIGH ENERGY PARTICLE ASTROPHYSICS, G7720562802, G7745284665, G7805626310, G7863371703, G8037394432, Galactic and Extragalactic Cosmic Rays, Neutrinos and Gamma Rays, G8140083606, G8146748976, G8262994006, G8497050386, G8560619796, G86560745, G8800403394, G8954508221, G969889393

OpenAlex ID: W7204451059

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