Highly-boosted dark matter and cutoff for cosmic-ray neutrino through neutrino portal

TL;DR

This paper explores how neutrino interactions with the cosmic background can create a cutoff in cosmic-ray neutrino flux, proposing a dark sector particle that can carry ultra-high energies across the universe.

Contribution

It introduces a viable neutrino portal interaction with the dark sector, especially coupled to tau neutrinos, affecting cosmic-ray neutrino propagation over cosmological distances.

Findings

Large interaction rates are possible with tau neutrino coupling.

Dark sector particles can carry energies up to EeV scale.

Neutrino mean free path can be reduced to about 10 Mpc.

Abstract

We study the cutoff for the cosmic-ray neutrino, set by the scattering with cosmic background neutrinos into dark sector particles through a neutrino portal interaction. We find that a large interaction rate is still viable, when the dark sector particles are mainly coupled to the $\tau-$neutrino, so that the neutrino mean free path can be reduced to be $O(10)~$Mpc over a wide energy range. If stable enough, the dark sector particle, into which most of the cosmic-ray neutrino energy is transferred, can travel across the Universe and reach the earth. The dark sector particle can carry the energy as large as $\O({\rm EeV})$ if originates from a cosmogenic neutrino.