Connecting cosmologically decaying dark matter to neutrino physics

Abstract

Dark matter decays into invisible particles can leave an imprint in large-scale structure surveys due to a characteristic redshift-dependent suppression of the power spectrum. We present a model with two quasi-degenerate singlet fermions, ${\chi }_1$ and ${\chi }_2$, in which the heavier state decays as ${\chi }_2\to {\bar{\chi }}_1\nu \nu$ on cosmological time-scales, and that also accommodates non-zero neutrino masses. Remarkably, for parameters that yield the correct dark matter abundance via freeze-in and reproduce the observed neutrino masses, dark matter decay can produce detectable signals in forthcoming large-scale structure surveys, a diffuse anti-neutrino flux accessible to JUNO, and a gamma-ray line within the energy range probed by COSI. Both the cosmological lifetime of ${\chi }_2$ as well as the small (radiatively induced) mass splitting among ${\chi }_{1,2}$ are a natural consequence of the mechanism of neutrino mass generation within this model. This highlights the potential role of large-scale structure surveys in probing some classes of neutrino mass models.

Comments: 15+10 pages, 9 figures, 2 tables