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 …

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

The existence of astrophysical neutrinos with energies of tens of TeV and higher has been
firmly established by the IceCube experiment; the first confirmations of this discovery were …

We critically examine the ability of future neutrino telescopes, including Baikal-GVD,
KM3NeT, P-ONE, TAMBO, and IceCube-Gen2, to determine the flavor composition of high …

Tau neutrinos are the least studied particle in the standard model. This whitepaper
discusses the current and expected upcoming status of tau neutrino physics with attention to …

We investigate the possibility that radio-bright active galactic nuclei (AGN) are responsible
for the TeV–PeV neutrinos detected by IceCube. We use an unbinned maximum-likelihood …

Ultrahigh-energy (UHE) neutrinos, with EeV-scale energies, carry with them unique insight
into fundamental open questions in astrophysics and particle physics. For 50 years, they …

Neutrinos offer a window to physics beyond the Standard Model. In particular, high-energy
astrophysical neutrinos, with TeV–PeV energies, may provide evidence of new,“secret” …

Detecting TeV–PeV cosmic neutrinos provides crucial tests of neutrino physics and
astrophysics. The statistics of IceCube and the larger proposed IceCube-Gen2 demand …