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 …

In this report we review the important progress made in recent years towards understanding
the experimental data on ultra-high-energy (E≳ 1 0 9 GeV) cosmic rays. We begin with a …

The Glashow resonance describes the resonant formation of a W− boson during the
interaction of a high-energy electron antineutrino with an electron, peaking at an …

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 …

We report a measurement of the energy spectrum of cosmic rays above 2.5× 10 18 eV
based on 215 030 events. New results are presented: at about 1.3× 10 19 eV, the spectral …

This article presents the design of the Radio Neutrino Observatory Greenland (RNO-G) and
discusses its scientific prospects. Using an array of radio sensors, RNO-G seeks to measure …

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 interaction of ultra-high-energy cosmic rays (UHECRs) with pervasive photon fields
generates associated cosmogenic fluxes of neutrinos and photons due to photohadronic …

The detection of the hyper-bright gamma-ray burst (GRB) 221009A enables us to explore
the nature of the GRB emission and the origin of very high-energy gamma rays. We analyze …