Studies of the UHECR Mass Composition and Hadronic Interactions with the FD and SD of the Pierre Auger Observatory

¹ Departamento de Física Teórica y del Cosmos, University of Granada, Granada, Spain.
² Full author list and acknowledgments at: http://www.auger.org/archive/authors_2018_09.html

^a e-mail: jmcarcell@ugr.es
^b e-mail: auger_spokespersons@fnal.gov

Published online: 13 May 2019

Abstract

With data on the depth of maximum X_max collected during more than a decade of operation of the Pierre Auger Observatory, we report on the inferences on the mass composition of UHECRs in the energy range E = 10^17.2 – 10^19.6 eV and on the measurements of the proton-air cross section for energies up to 10^18.5 eV. We also present the results on X_max obtained using the information on the particle arrival times recorded by the SD stations allowing us to extend the X_max measurements up to 10²⁰ eV. The inferences on mass composition, in particular using the data of the SD, are subject to systematic uncertainties due to uncertainties in the description of hadronic interactions at ultra-high energies. We discuss this problem with respect to the properties of the muonic component of extensive air-showers as derived from the SD data.