Inference of the Mass Composition of Cosmic Rays with energies from $10^{18.5}$ to $10^{20}$ eV using the Pierre Auger Observatory and Deep Learning

Abstract

We present measurements of the atmospheric depth of the shower maximum $X_{\max }$, 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 $X_{\max }$ 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 $X_{\max }$ with the logarithm of energy features three breaks at $6.5\pm 0.6(\mathrm{stat})\pm 1(\mathrm{sys})$ EeV, $11\pm 2(\mathrm{stat})\pm 1(\mathrm{sys})$ EeV, and $31\pm 5(\mathrm{stat})\pm 3(\mathrm{sys})$ 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 $X_{\max }$ 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.

Version accepted for publication in Phys. Rev. Lett., 9 pages, 3 figures, 1 table

References in corpus (18)

• Depth of Maximum of Air-Shower Profiles at the Pierre Auger Observatory: Measurements at Energies above 10^17.8 eV
• Observation of high-energy neutrinos from the Galactic plane
• Measurement of the proton-air cross-section at $\sqrt{s}=57$ TeV with the Pierre Auger Observatory
• The Cosmic Ray Energy Spectrum Observed with the Surface Detector of the Telescope Array Experiment
• Testing Hadronic Interactions at Ultrahigh Energies with Air Showers Measured by the Pierre Auger Observatory
• Features of the energy spectrum of cosmic rays above $2.5\times 10^{18}$ eV using the Pierre Auger Observatory
• The energy spectrum of cosmic rays beyond the turn-down around $10^{17}$ eV as measured with the surface detector of the Pierre Auger Observatory
• AugerPrime: the Pierre Auger Observatory Upgrade
• Measurement of the fluctuations in the number of muons in extensive air showers with the Pierre Auger Observatory
• A Deep Learning-based Reconstruction of Cosmic Ray-induced Air Showers
• Constraining the sources of ultra-high-energy cosmic rays across and above the ankle with the spectrum and composition data measured at the Pierre Auger Observatory
• A Convolutional Neural Network based Cascade Reconstruction for the IceCube Neutrino Observatory
• Event reconstruction for KM3NeT/ORCA using convolutional neural networks
• Deep-Learning based Reconstruction of the Shower Maximum $X_{\max }$ using the Water-Cherenkov Detectors of the Pierre Auger Observatory
• Reconstruction of Events Recorded with the Surface Detector of the Pierre Auger Observatory
• Extraction of the Muon Signals Recorded with the Surface Detector of the Pierre Auger Observatory Using Recurrent Neural Networks
• Testing Hadronic-Model Predictions of Depth of Maximum of Air-Shower Profiles and Ground-Particle Signals using Hybrid Data of the Pierre Auger Observatory
• 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

Cited by in corpus (15)

• 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
• Ultra-high-energy cosmic rays from ultra-fast outflows of active galactic nuclei
• Cosmic-Ray Constraints on the Flux of Ultra-High-Energy Neutrino Event KM3-230213A
• A LOFAR-style reconstruction of cosmic-ray air showers with SKA-Low
• Ultraheavy Ultrahigh-Energy Cosmic Rays
• Ultrahigh energy cosmic rays and neutrino flux models
• A Heavy-Metal Scenario of Ultra-High-Energy Cosmic Rays
• Discriminating sub-TeV gamma and hadron-induced showers through their footprints
• Application of Graph Networks to a wide-field Water-Cherenkov-based Gamma-Ray Observatory
• The Sensitivity of PUEO to Cosmogenic Neutrinos and Exotic Physics Scenarios
• Event Reconstruction for Radio-Based In-Ice Neutrino Detectors with Neural Posterior Estimation
• Beyond the Local Void: A data-driven search for the origins of the Amaterasu particle
• A Unified Framework for 10 TeV to EeV Diffuse Neutrino Sky and KM3-230213A
• Recent advances on multimessenger astrophysics: Centaurus A, GW 170817, and KM3-230213A
• Possible Sources of Iron Nuclei in Ultra-High-Energy Cosmic Rays