IceCube events and decaying dark matter: hints and constraints

TL;DR

This paper updates the analysis of IceCube neutrino data to evaluate the decaying dark matter hypothesis, finding a mild statistical preference for dark matter decay angular distribution and setting new constraints on dark matter properties.

Contribution

It develops advanced angular distribution analysis and statistical tests to assess dark matter decay as the source of IceCube neutrinos, providing improved bounds on dark matter lifetime.

Findings

Mild preference for dark matter decay angular distribution over isotropic flux.

Lower limits on heavy dark matter lifetime are improved by up to an order of magnitude.

Constraints on dark matter models are strengthened, impacting future astroparticle physics research.

Abstract

In the light of the new IceCube data on the (yet unidentified) astrophysical neutrino flux in the PeV and sub-PeV range, we present an update on the status of decaying dark matter interpretation of the events. In particular, we develop further the angular distribution analysis and discuss the perspectives for diagnostics. By performing various statistical tests (maximum likelihood, Kolmogorov-Smirnov and Anderson-Darling tests) we conclude that currently the data show a mild preference (below the two sigma level) for the angular distribution expected from dark matter decay vs. the isotropic distribution foreseen for a conventional astrophysical flux of extragalactic origin. Also, we briefly develop some general considerations on heavy dark matter model building and on the compatibility of the expected energy spectrum of decay products with the IceCube data, as well as with existing bounds from gamma-rays. Alternatively, assuming that the IceCube data originate from conventional astrophysical sources, we derive bounds on both decaying and annihilating dark matter for various final states. The lower limits on heavy dark matter lifetime improve by up to an order of magnitude with respect to existing constraints, definitively making these events---even if astrophysical in origin---an important tool for astroparticle physics studies.