Upper limits on the cosmic neutrino background from cosmic rays

Abstract

Extragalactic and galactic cosmic rays scatter with the cosmic neutrino background during propagation to Earth, yielding a flux of relic neutrinos boosted to larger energies. If an overdensity of relic neutrinos is present in galaxies, and neutrinos are massive enough, this flux might be detectable by high-energy neutrino experiments. For a lightest neutrino of mass m(nu)similar to 0.1 eV, we find an upper limit on the local relic neutrino overdensity of similar to 10(13) and an upper limit on the relic neutrino overdensity at TXS 0506+056 of similar to 10(10). Future experiments like GRAND or IceCube-Gen2 could improve these bounds by orders of magnitude.