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 …

We report a measurement of the energy spectrum of cosmic rays for energies above 2.5× 10
18 eV based on 215,030 events recorded with zenith angles below 60. A key feature of the …

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 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 …

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 Large Hadron–Electron Collider (LHeC) is designed to move the field of deep
inelastic scattering (DIS) to the energy and intensity frontier of particle physics. Exploiting …

We report a study of the distributions of the depth of maximum, X max, of extensive air-
shower profiles with energies above 1 0 17.8 eV as observed with the fluorescence …

A new analysis of the data set from the Pierre Auger Observatory provides evidence for
anisotropy in the arrival directions of ultra-high-energy cosmic rays on an intermediate …