Implications of cosmic ray results for UHE neutrinos

TL;DR

This paper discusses how recent cosmic ray measurements impact expectations for ultrahigh energy neutrino fluxes, the requirements for neutrino detectors, and the potential for new physics insights into QCD at high energies.

Contribution

It highlights the implications of heavy nuclei in cosmic rays for neutrino flux predictions and detector design, and explores the potential for ultrahigh energy neutrino interactions to probe QCD.

Findings

Heavy nuclei in cosmic rays can suppress neutrino fluxes.

Neutrino detectors may need to be larger than current plans.

Ultrahigh energy neutrino interactions can probe high-density QCD.

Abstract

Recent measurements of the spectrum and composition of ultrahigh energy cosmic rays suggest that their extragalactic sources may be accelerating heavy nuclei in addition to protons. This can suppress the cosmogenic neutrino flux relative to the usual expectation for an all-proton composition. Cosmic neutrino detectors may therefore need to be even larger than currently planned but conversely they will also be able to provide valuable information concerning astrophysical accelerators. Moreover measurement of ultrahigh energy cosmic neutrino interactions can provide an unique probe of QCD dynamics at high parton density.