IceCube neutrinos, decaying dark matter, and the Hubble constant

TL;DR

This paper proposes that decaying superheavy dark matter can explain the extraterrestrial neutrino flux observed by IceCube and reconcile cosmological parameter tensions, with testable predictions for future IceCube observations.

Contribution

It introduces a model where dark matter decay into neutrinos accounts for IceCube flux and cosmological discrepancies, providing specific branching ratios and testable predictions.

Findings

Decaying dark matter can produce the observed neutrino flux.

Future IceCube data can distinguish the decay signal.

The model can reconcile Planck and low-redshift cosmological measurements.

Abstract

Cosmological parameters deduced from the Planck measurements of anisotropies in the cosmic microwave background are at some tension with direct astronomical measurements of various parameters at low redshifts. Very recently, it has been conjectured that this discrepancy can be reconciled if a certain fraction of dark matter is unstable and decays between recombination and the present epoch. Herein we show that if the superheavy relics have a branching into neutrinos B (X \to \nu \bar \nu) \sim 3 \times 10^{-9}, then this scenario can also accommodate the recently discovered extraterrestrial flux of neutrinos, relaxing the tension between IceCube results and Fermi LAT data. The model is fully predictive and can be confronted with future IceCube data. We demonstrate that in 10 years of observation IceCube will be able to distinguish the mono-energetic signal from X decay at the 3\sigma level. In a few years of data taking with the upgraded IceCube-Gen2 enough statistics will be gathered to elucidate the dark matter--neutrino connection at the 5\sigma level.