Ultra-High Energy Cosmic Ray and Neutrino Observations

TL;DR

Recent advancements in large-scale observatories have provided high-quality data on ultra-high energy cosmic rays and neutrinos, offering new insights into their origins, interactions, and fundamental physics, despite still lacking definitive source identification.

Contribution

The paper reviews recent observational progress and highlights the potential of upcoming large-volume neutrino telescopes to uncover the origins of the highest energy particles.

Findings

First full-sky neutrino views from multiple hemispheres.

Constraints on neutrino fluxes from various sources.

Initial data suggest new physics and astrophysical insights.

Abstract

Recent measurements of ultra-high energy cosmic rays and neutrinos are briefly reviewed. With several new large scale observatories nearing completion or becoming fully operational only very recently, a large body of high quality and high statistics data is growing up now. Already these first data have started to open up a new window to the high energy Universe giving us first direct clues about the origin of the most energetic particles with energies of about 10^{20} eV as well as about their interactions from extragalactic sources to Earth. Also, for the first time full sky views of high energy neutrinos have become available with neutrino telescopes operating on either Hemisphere. While a "smoking gun" is still missing on galactic sources of cosmic rays, constraining upper limits to neutrino fluxes from various source candidates are reported. Thus, future neutrino telescopes, such as KM3NeT in the Mediterranean should aim at volumes significantly larger than one cubic kilometer. Besides seeking the sources of galactic and extragalactic cosmic rays, the new generation of cosmic ray and neutrino observatories touches a wide range of scientific issues and they have already provided important results on tests of fundamental physics.