Speaker
Description
The Pierre Auger Observatory is the largest detector for measuring ultra-high-energy cosmic rays. Located in Argentina and spanning over 3000 square kilometers, the Observatory samples the particle content of Extensive Air Showers using an array of Water-Cherenkov Detectors (WCDs). The shower longitudinal profile is measured with Fluorescence Detectors. In this contribution, the interpretations of the mass composition of ultra-high-energy cosmic ray flux based on data collected by the Pierre Auger Observatory are reviewed. Moreover, we present the evolution of the mean mass of cosmic ray primaries with primary energy, using independent measurements of the depth of the shower maximum, $X_{\max}$, made with various detectors of the Observatory, including the Auger Engineering Radio Array (AERA). Additionally, we highlight the recent results from deep neural networks trained on WCD data, which enabled a tenfold increase in statistics at the highest energies, providing unprecedented precision for mass estimation at these energies. The tension between the mass composition inferred from $X_{\max}$ and other shower observables is addressed. Finally, we examine the potential of AugerPrime, the upgrade of the Pierre Auger Observatory, to improve the precision of mass composition measurements.
