Probing self-interacting ultrahigh-energy neutrinos with the cosmic 21-cm signal

TL;DR

This paper explores how the 21-cm hydrogen signal during cosmic dark ages can constrain self-interacting ultrahigh-energy neutrinos, offering more competitive limits than existing experiments and insights into dark matter and neutrino physics.

Contribution

It introduces a novel method to constrain neutrino self-interactions using the cosmic 21-cm signal during dark ages and dawn, with tighter bounds than previous astrophysical and collider constraints.

Findings

Constraints on neutrino coupling constant g are between 10^{-4} and 10^{-3}.

21-cm observations can provide competitive bounds on neutrino interactions.

Future 21-cm experiments could probe neutrino properties across cosmic history.

Abstract

In this study, we investigate the constraints on secret self-interactions of neutrinos by examining the impact of radiative scattering of ultrahigh-energy neutrinos. These neutrinos are produced from the decay of superheavy dark matter and interact with the cosmic neutrino background. We explore how these interactions influence the 21-cm hydrogen signal during the cosmic dark ages and cosmic dawn, periods relatively free from astrophysical uncertainties, providing a clearer signal for studying nonstandard neutrino interactions. By analyzing the global brightness temperature measurements, we constrain the scattering cross section of ultrahigh-energy self-interacting neutrinos, determining the coupling constant $g$ to be within $\sim 10^{-4}$ to $\sim 10^{-3}$ for neutrino energies in the PeV to EeV range. Interestingly, these constraints are more competitive than those from existing astrophysical and collider experiments. As future 21-cm experiments focus on measuring brightness temperature across a wide range of redshifts from the cosmic dark ages to reionization, using the epoch of 21-cm to probe neutrino properties could provide crucial insights into dark matter and neutrino physics.