The exploration of the universe has recently entered a new era thanks to the multi-
messenger paradigm, characterized by a continuous increase in the quantity and quality of …

We review open questions and prospects for progress in ultrahigh-energy cosmic ray
(UHECR) research, based on a series of discussions that took place during the “The High …

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 atomic nuclei arriving from outer space that reach the highest energies
observed in nature. Clues to their origin come from studying the distribution of their arrival …

We present the simulation framework CRPropa version 3 designed for efficient development
of astrophysical predictions for ultra-high energy particles. Users can assemble modules of …

In this work we present the interpretation of the energy spectrum and mass composition data
as measured by the Pierre Auger Collaboration above 6× 1017 eV. We use an astrophysical …

Abstract The Pierre Auger Observatory, located on a vast, high plain in western Argentina, is
the world׳ s largest cosmic ray observatory. The objectives of the Observatory are to probe …

The distribution of the arrival directions of cosmic rays (CR) with ultrahigh energies is
expected to play a major role in the quest to unveil the origin of these particles. Hints of …

The Pierre Auger Observatory has begun a major Upgrade of its already impressive
capabilities, with an emphasis on improved mass composition determination using the …

The discovery of high-energy astrophysical neutrinos and the first hints of coincident
electromagnetic and neutrino emissions opened new opportunities in multi-messenger …