The Milky Way is a Laboratory for New Ultra-long-baseline Neutrino Physics

TL;DR

This paper investigates how astrophysical neutrinos from the Galactic Plane can be used to test ultra-long-baseline neutrino physics, such as tiny mass splittings and neutrino decay, with current and future detectors.

Contribution

It introduces a new sensitivity analysis using a galactic neutrino emission model to explore untested parameter space in neutrino mass and decay models.

Findings

Sensitivity to quasi-Dirac mass splittings over many orders of magnitude

Potential to probe neutrino lifetimes beyond current limits

Demonstrates astrophysical neutrinos' role in new physics searches

Abstract

The IceCube Neutrino Observatory recently published evidence for diffuse neutrino emission from the Galactic Plane at $4.5\sigma$ significance. This new source of astrophysical neutrinos provides an exciting laboratory for probing the nature of neutrino masses. In particular, extremely small mass splittings, such as those predicted by quasi-Dirac neutrino mass models, and finite neutrino lifetimes from neutrino decays, would induce effects on the spectra and flavor ratios of neutrinos with TeV-scale energies traversing kiloparsec-scale baselines. Using $\mathtt{TANDEM}$, an upcoming three dimensional galactic neutrino emission model, we explore the sensitivity of IceCube and KM3NeT/ARCA to these ultra-long-baseline phenomena. We find that a combined analysis would be sensitive to quasi-Dirac mass splittings $10^{-14.0}~\mathrm{eV^2} \lesssim \delta m^2 \lesssim 10^{11.6}~\mathrm{eV^2}$ and neutrino lifetimes $m / \tau \gtrsim 10^{-14.1}~\mathrm{eV^2}$ at $> 1\sigma$, both regions constituting as-yet unexplored parameter space. Our results demonstrate the potential that astrophysical neutrino sources and global neutrino telescope networks have in probing new regions of exotic neutrino mass models.