Neutrino secret self-interactions: a booster shot for the cosmic neutrino background

TL;DR

This paper explores hypothetical neutrino self-interactions that could boost the cosmic neutrino background to detectable energies, deriving constraints from current experiments and assessing future detection prospects.

Contribution

It introduces a model-independent analysis of neutrino self-interactions and evaluates their impact on the cosmic neutrino background and detection feasibility.

Findings

Current constraints make boosted CνB contribution negligible.

Upscattered neutrino flux is too small for detection with existing experiments.

Future detection of boosted CνB appears unlikely under current bounds.

Abstract

Neutrinos might interact among themselves through forces that have so far remained hidden. Throughout the history of the Universe, such \emph{secret} interactions could lead to scatterings between the neutrinos from supernova explosions and the non-relativistic relic neutrinos left over from the Big Bang. Such scatterings can boost the cosmic neutrino background (C$\nu$B) to energies of ${\cal O}$(MeV), making it, in principle, observable in experiments searching for the diffuse supernova neutrino background. Assuming a model-independent, but flavor universal, four-Fermi interaction, we determine the upscattered cosmic neutrino flux, and derive constraints on such secret interactions from the latest results from Super-Kamiokande. Furthermore, we also study prospects for detection of the boosted flux in future lead-based coherent elastic neutrino-nucleus scattering experiments. Nevertheless, given current constraints on flavor universal self-interactions, we find that the upscattered C$\nu$B~contribution to the total DSNB flux is negligible, making a possible measurement of the boosted C$\nu$B insurmountable.