Cosmic PeV Neutrinos and the Sources of Ultrahigh Energy Protons

TL;DR

This paper investigates whether the high-energy neutrinos detected by IceCube originate from the same extragalactic sources as ultrahigh-energy cosmic rays, finding that typical pion photoproduction models struggle to produce the observed neutrino flux without suppressing cosmic-ray flux.

Contribution

It introduces a general analysis linking high-energy neutrino fluxes to cosmic-ray sources, highlighting the need for specific conditions in accelerators to reconcile observations.

Findings

Neutrino flux from pion photoproduction is insufficient unless pions/muons cool before decay.

Typical models predict proton fluxes below observed cosmic-ray levels at 10^18 eV.

Certain accelerator conditions are necessary for cosmic rays to escape without producing excessive neutrinos.

Abstract

The IceCube experiment recently detected the first flux of high-energy neutrinos in excess of atmospheric backgrounds. We examine whether these neutrinos originate from within the same extragalactic sources as ultrahigh-energy cosmic rays. Starting from rather general assumptions about spectra and flavors, we find that producing a neutrino flux at the requisite level through pion photoproduction leads to a flux of protons well below the cosmic-ray data at ~10^18 eV, where the composition is light, unless pions/muons cool before decaying. This suggests a dominant class of accelerator that allows for cosmic rays to escape without significant neutrino yields.