Dark Matter-Enhanced Probe of Relic Neutrino Clustering

Abstract

The existence of the relic neutrino background is a strong prediction of the Big Bang cosmology. But because of their extremely small kinetic energy today, the direct detection of relic neutrinos remains elusive. On the other hand, we know very little about the nature of dark matter. In this work, we propose heavy decaying neutrinophilic dark matter (DM) as a new probe of the cosmic neutrino background. Including the contribution of neutrinos resulting from DM-decay along with the measured astrophysical and predicted cosmogenic neutrino fluxes, we study the scattering of ultra high energy (UHE) neutrinos with the relic neutrino background via standard weak interactions mediated by the Z-boson and calculate the expected spectrum of this UHE neutrino flux at future neutrino telescopes, such as IceCube-Gen2 Radio. Observations of such scattered UHE neutrino flux can be used to probe the Cosmic neutrino background properties, and specifically, its local clustering. We find that, depending on the absolute neutrino mass and the DM mass and lifetime, a local relic neutrino overdensity around 1e6 can be probed at IceCube-Gen2 Radio within 10 years of data taking.

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