Dynamic Neutrino Mass Ordering and Its Imprint on the Diffuse Supernova Neutrino Background

Abstract

Neutrino masses may have evolved dynamically throughout the history of the Universe, potentially leading to a mass spectrum distinct from the normal or inverted ordering observed today. While cosmological measurements constrain the total energy density of neutrinos, they are not directly sensitive to a dynamically changing mass ordering unless future surveys achieve exceptional precision in detecting the distinct imprints of each mass eigenstate on large-scale structures. In this work, we investigate the impact of a dynamic neutrino mass spectrum on the diffuse supernova neutrino background (DSNB), which is composed of neutrinos from all supernova explosions throughout cosmic history and is on the verge of experimental detection. The dynamic evolution of neutrino masses with redshift changes the propagation of neutrinos inside the supernova. Since neutrino oscillations are highly sensitive to the mass spectrum, we show that the electron neutrino survival probability carries distinct signatures of the evolving neutrino mass spectrum. Our results show that a dynamic neutrino mass spectrum can modify the DSNB flux in an energy-dependent way. However, we find that the current level of spectral shape uncertainty in DSNB modeling makes a direct detection beyond the reach of present and near-future experiments. Nonetheless, our study highlights the DSNB as a probe of redshift-dependent neutrino properties once the astrophysical systematics are brought under control.