The present white paper is submitted as part of the “Snowmass” process to help inform the
long-term plans of the United States Department of Energy and the National Science …

Cosmic rays are relativistic particles that come to the Earth from outer space. Despite a great
effort made in both experimental and theoretical research, their origin is still unknown. One …

We test the predictions of hadronic interaction models regarding the depth of maximum of air-
shower profiles, X max, and ground-particle signals in water-Cherenkov detectors at 1000 m …

Abstract The Pierre Auger Observatory has been detecting ultra-high energy cosmic rays
(UHECRs) for more than fifteen years. An essential feature of the Observatory is its hybrid …

The direction and magnitude of the dipole anisotropy of ultra-high-energy cosmic rays with
energies above 8 EeV observed by the Pierre Auger Observatory indicate their extragalactic …

The deficit of muons in the simulation of extensive air showers is a long-standing problem
and the origin of large uncertainties in the reconstruction of the mass of the high-energy …

Presently large systematic uncertainties remain in the description of hadronic interactions at
ultra-high energies and a fully consistent description of air-shower experimental data is yet …

We present a method for testing the predictions of hadronic interaction models and
improving their consistency with observed two-dimensional distributions of the depth of …

The scientific achievements of the Pierre Auger Collaboration cover diverse and
complementary fields of research. The search for the origin of ultra-high energy cosmic rays …

Ultra-high-energy (E> 1018 electron volts) cosmic rays (UHECRs) are the highest energy
particles ever detected by human beings. Decades of measurements have revealed that …