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 observation of electromagnetic radiation from radio to γ-ray wavelengths has provided a
wealth of information about the Universe. However, at PeV (10 15 eV) energies and above …

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 …

Abstract The Probe Of Extreme Multi-Messenger Astrophysics (POEMMA) is designed to
accurately observe ultra-high-energy cosmic rays (UHECRs) and cosmic neutrinos from …

Astrophysical neutrinos are excellent probes of astroparticle physics and high-energy
physics. With energies far beyond solar, supernovae, atmospheric, and accelerator …

Abstract The Giant Radio Array for Neutrino Detection (GRAND) is a planned large-scale
observatory of ultra-high-energy (UHE) cosmic particles, with energies exceeding 10 8 GeV …

The dominant neutrino fluxes at Earth from different sources are reviewed and the grand
unified neutrino spectrum ranging from meV to PeV energies is presented. For each energy …

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 …

The landscape of high-and ultra-high-energy astrophysics has changed in the last decade,
largely due to the inflow of data collected by large-scale cosmic-ray, gamma-ray, and …