Paper

Measurement of the Depth of Maximum of Air-Shower Profiles with energies between \\(10^18.5\\) and \\(10^20\\) eV using the Surface Detector of the Pierre Auger Observatory and Deep Learning

Stanič, S, Simon, F, Coluccia, M R, Paulsen, T, Querchfeld, S, de Oliveira Franco, D, Filipčič, A, Palatka, M, Pawlowsky, J, González, N, Rizi, V, Shivashankara, S U, Luce, Q, Caruso, R, García, B, Pothast, M, Mandat, D, Supanitsky, A D, Gongora, J P, Nguyen, K, Convenga, F, Dasso, S, Rossoni, S, Watson, A A, Avila, G, Rovero, A C, Tairli, F, Matthews, J, Wundheiler, B, Medina-Tanco, G, O Martínez Bravo, Schulz, T, Gülzow, L, Janecek, P, Pękala, J, Fauth, A C, Mollerach, S, Pech, M, Pimenta, M, Fuster, A, de Oliveira, J, Feldbusch, F, Taricco, C, Schieler, H, Figueira, J M, Sigl, G, Majercakova, M, Binet, V, de Almeida, R M, Etchegoyen, A, Schimassek, M, Salina, G, Simkova, K, Góra, D, Smau, R, Falcke, H, Flaggs, B, V V Kizakke Covilakam, De Vito, E, Dorosti, Q, Bonifazi, C, Pereira Martins, E E, González, J M, Hansen, P, Squartini, R, Mariani, F M, Guarino, F, Prouza, M, Khakurdikar, A, Fernandes, A, Aramo, C, Jurysek, J, Sarazin, F, Niechciol, M, Mayotte, E, Condorelli, A, Klages, H O, Correia dos Santos, D, Fujii, T, Hampel, M R, Roncoroni, M J, Caccianiga, L, Fodran, T, Denner, N, Sciutto, S J, Abreu, P, Rodrigues de Carvalho, W, Mayotte, S, Boncioli, D, C

2025

Overview

We report an investigation of the mass composition of cosmic rays with energies from 3 to 100 EeV (1 EeV=\\(10^18\\) eV) using the distributions of the depth of shower maximum \\(X_max\\). The analysis relies on \\(50,000\\) events recorded by the Surface Detector of the Pierre Auger Observatory and a deep-learning-based reconstruction algorithm. Above energies of 5 EeV, the data set offers a 10-fold increase in statistics with respect to fluorescence measurements at the Observatory. After cross-calibration using the Fluorescence Detector, this enables the first measurement of the evolution of the mean and the standard deviation of the \\(X_max\\) distributions up to 100 EeV. Our findings are threefold: (1.) The evolution of the mean logarithmic mass towards a heavier composition with increasing energy can be confirmed and is extended to 100 EeV. (2.) The evolution of the fluctuations of \\(X_max\\) towards a heavier and purer composition with increasing energy can be confirmed with high statistics. We report a rather heavy composition and small fluctuations in \\(X_max\\) at the highest energies. (3.) We find indications for a characteristic structure beyond a constant change in the mean logarithmic mass, featuring three breaks that are observed in proximity to the ankle, instep, and suppression features in the energy spectrum.

• Publisher: Cornell University Library, arXiv.org
• Subject: Composition / Cosmic ray showers / Cosmic rays / Deep learning / Energy spectra / Evolution / Fluorescence / Logarithms / Machine learning / Mean / Observatories / Sensors / Surface detectors