Constraining the pseudo-Dirac nature of neutrinos using astrophysical neutrino flavor data

TL;DR

This paper explores how astrophysical neutrino flavor data can be used to constrain the pseudo-Dirac nature of neutrinos, providing bounds on mass splittings that could distinguish between different neutrino mass models.

Contribution

It introduces a method to use astrophysical neutrino flavor ratios to set bounds on pseudo-Dirac neutrino mass splittings, improving sensitivity with future experiments and source knowledge.

Findings

Robust bounds of order 10^{-12} eV^2 on mass splittings with IceCube-Gen2.

Potential to improve bounds to 10^{-17} eV^2 if source information is available.

Sensitivity depends only on extragalactic origin and hierarchical spectrum assumptions.

Abstract

The three Standard Model neutrinos can have Majorana mass or strictly Dirac mass, but both scenarios are practically indistinguishable in neutrino oscillation experiments. If they are pseudo-Dirac, however, there will be new mass splittings among the pseudo-Dirac pairs, potentially leaving traces in neutrino oscillation phenomena. In this work, we use flavor ratios of astrophysical neutrinos to discriminate different possible mass spectra of pseudo-Dirac neutrinos. We show that it will be possible to impose robust bounds of order $\delta m^2_3 \lesssim 10^{-12}$ $\text{eV}^2$ on the new mass squared splitting involving the third pseudo-Dirac mass eigenstates (those with the least electron flavor composition) with the future experiment IceCube-Gen2. The derived sensitivity is robust because it only assumes an extragalactic origin for the astrophysical neutrinos and hierarchical pseudo-Dirac mass spectrum. In case the neutrino sources are known in the future, such bounds can potentially improve by up to five orders of magnitude, reaching $\delta m^2_3 \lesssim 10^{-17}$ $\text{eV}^2$.