Neutrino Background Flux from Sources of Ultrahigh-Energy Cosmic-Ray Nuclei

TL;DR

This paper explores the neutrino background flux resulting from ultrahigh-energy cosmic-ray nuclei, showing it is lower than proton-based predictions and discussing implications for IceCube neutrino observations.

Contribution

It provides the first detailed estimate of neutrino flux from UHE nuclei considering photodisintegration constraints, highlighting differences from proton-based models.

Findings

Neutrino flux from UHE nuclei is below IceCube sensitivity.

Photodisintegration limits reduce neutrino production in sources.

Detection of neutrinos would suggest alternative cosmic-ray source processes.

Abstract

Motivated by Pierre Auger Observatory results favoring a heavy nuclear composition for ultrahigh-energy (UHE) cosmic rays, we investigate implications for the cumulative neutrino background. The requirement that nuclei not be photodisintegrated constrains their interactions in sources, therefore limiting neutrino production via photomeson interactions. Assuming a $dN_{\rm CR}/dE_{\rm CR} \propto E_{\rm CR}^{-2}$ injection spectrum and photodisintegration via the giant dipole resonance, the background flux of neutrinos is lower than $E_\nu^2 \Phi_\nu \sim {10}^{-9} {\rm GeV} {\rm cm}^{-2} {\rm s}^{-1} {\rm sr}^{-1}$ if UHE nuclei ubiquitously survive in their sources. This is smaller than the analogous Waxman-Bahcall flux for UHE protons by about one order of magnitude, and is below the projected IceCube sensitivity. If IceCube detects a neutrino background, it could be due to other sources, e.g., hadronuclear interactions of lower-energy cosmic rays; if it does not, this supports our strong restrictions on the properties of sources of UHE nuclei.