2025/10/17 by Nicola Terzaghi, Terzaghi, Nicola, Guillermo Franco Abellán +5 · 1 citation
Physics and Astronomy · #Neutrino Physics Research #Particle physics theoretical and experimental studies #Dark Matter and Cosmic Phenomena
paper · pdf · doi:10.48550/arxiv.2510.15818
The anisotropies of the Cosmic Neutrino Background (CνB) offer an ideal tool to test non-standard neutrino interactions, since they directly trace the perturbations in the neutrino distribution function. Here, we study how invisible neutrino decays impact the CνB anisotropies, in a framework where neutrinos decay non-relativistically to dark radiation and lighter neutrinos in a manner consistent with the measured mass splittings. For this purpose, we perform the first implementation of such a late-time neutrino decay scenario within a linear Einstein-Boltzmann solver, and compute the CνB angular power spectra from the Boltzmann hierarchy solutions for a range of lifetimes and decay channels. We find that neutrino decays leave very strong signatures on the CνB angular spectra, about two orders of magnitude larger than on the CMB angular spectra, particularly for lifetimes comparable to the age of the Universe. We show that a future polarized tritium target run of the PTOLEMY experiment, with sufficient counting statistics to measure just the first ∼ 15 multipoles of the neutrino sky map, could test neutrino decay models that remain undetectable with CMB data.