The Unknowns of the Diffuse Supernova Neutrino Background Hinder New Physics Searches

TL;DR

The paper discusses how uncertainties in modeling the diffuse supernova neutrino background (DSNB) and experimental backgrounds limit the ability to detect new physics, like neutrino decay, with upcoming neutrino observatories.

Contribution

It analyzes the impact of astrophysical uncertainties and detector backgrounds on the potential to identify new physics through DSNB observations, highlighting current limitations.

Findings

Next-generation detectors can set stringent limits on neutrino lifetime if backgrounds are controlled.

Constraining visible decay is difficult if the lightest neutrino is nearly massless and mass ordering is normal.

Differentiating among new physics scenarios remains challenging due to similar DSNB signatures.

Abstract

Neutrinos traveling over cosmic distances are ideal probes of new physics. We leverage on the approaching detection of the diffuse supernova neutrino background (DSNB) to explore whether, if the DSNB showed departures from theoretical predictions, we could attribute such modifications to new physics unequivocally. In order to do so, we focus on visible neutrino decay. Many of the signatures from neutrino decay are degenerate with astrophysical unknowns entering the DSNB modeling. Next generation neutrino observatories, such as Hyper-Kamiokande, JUNO, as well as DUNE, will set stringent limits on a neutrino lifetime over mass ratio $\tau/m \sim 10^{9}$-$10^{10}$ s eV$^{-1}$ at $90\%$ C.L., if astrophysical uncertainties and detector backgrounds were to be fully under control. However, if the lightest neutrino is almost massless and the neutrino mass ordering is normal, constraining visible decay will not be realistically possible in the coming few decades. We also assess the challenges of distinguishing among different new physics scenarios (such as visible decay, invisible decay, and quasi-Dirac neutrinos), all leading up to similar signatures in the DSNB. This work shows that the DSNB potential for probing new physics strongly depends on an improved understanding of the experimental backgrounds at next generation neutrino observatories as well as progress in the DSNB modeling.