The diffuse supernova neutrino background as a probe of late-time neutrino mass generation

TL;DR

This paper explores how the diffuse supernova neutrino background (DSNB) can reveal if neutrino masses have changed over cosmic time, especially at redshifts up to 5, by analyzing the energy spectra of neutrinos and antineutrinos.

Contribution

It introduces a phenomenological model of redshift-dependent neutrino masses and predicts how the DSNB spectra could indicate late-time neutrino mass generation.

Findings

The electron neutrino spectrum could differ significantly from standard models if neutrinos were massless at high redshifts.

The antineutrino flux is less affected by changes in neutrino mass over cosmic time.

Measuring both neutrino and antineutrino spectra can test theories of recent neutrino mass generation.

Abstract

The relic neutrinos from old supernova explosions are among the most ancient neutrino fluxes within experimental reach. Thus, the diffuse supernova neutrino background (DSNB) could teach us if neutrino masses were different in the past (redshifts $z\lesssim 5$). Oscillations inside the supernova depend strongly on the neutrino mass-squared differences and the values of the mixing angles, rendering the DSNB energy spectrum sensitive to variations of these parameters. Considering a purely phenomenological parameterization of the neutrino masses as a function of redshift, we compute the expected local DSNB spectrum here on Earth. Given the current knowledge of neutrino oscillation parameters, specially the fact that $|U_{e3}|^2$ is small, we find that the $\nu_e$ spectrum could be significantly different from standard expectations if neutrinos were effectively massless at $z\gtrsim1$ as long as the neutrino mass ordering is normal. On the other hand, the $\overline{\nu}_e$ flux is not expected to be significantly impacted. Hence, a measurement of both the neutrino and antineutrino components of the DSNB should allow one to test the possibility of recent neutrino mass generation.