Search for neutrinos from decaying dark matter with IceCube (1804.03848v2)

Abstract: With the observation of high-energy astrophysical neutrinos by the IceCube Neutrino Observatory, interest has risen in models of PeV-mass decaying dark matter particles to explain the observed flux. We present two dedicated experimental analyses to test this hypothesis. One analysis uses six years of IceCube data focusing on muon neutrino 'track' events from the Northern Hemisphere, while the second analysis uses two years of 'cascade' events from the full sky. Known background components and the hypothetical flux from unstable dark matter are fitted to the experimental data. Since no significant excess is observed in either analysis, lower limits on the lifetime of dark matter particles are derived: We obtain the strongest constraint to date, excluding lifetimes shorter than $10^{28}\,$s at $90\%$ CL for dark matter masses above $10\,$TeV.

Analysis of Neutrino Observations for Decaying Dark Matter Signatures with IceCube

The research paper, authored by the IceCube Collaboration, explores the hypothesis that high-energy neutrinos detected by the IceCube Neutrino Observatory might originate from the decay of massive dark matter particles. This paper is predicated on the potential link between the high-energy neutrino flux and decaying heavy dark matter (DM), particularly in light of the lack of new discoveries in weakly interacting massive particles (WIMP) searches.

Experimental Methodology

The IceCube Neutrino Observatory at the South Pole, which detects Cherenkov radiation from charged particles produced in neutrino interactions in ice, is leveraged to investigate this hypothesis. Two separate datasets were analyzed:

1. Muon Neutrino (Track) Events: Spanning from 2009 to 2015, this dataset includes upward-going muon neutrino events from the Northern Hemisphere.
2. Cascade Events: Covering 2010 to 2012, this dataset considers full-sky cascade events from all neutrino flavors.

Both samples are statistically independent, with track events offering a larger dataset but cascade events providing better energy resolution and sky coverage.

Analytical Approach

The analysis utilizes a forward-folding likelihood method to fit the observed neutrino spectra. The proposed origins of these spectra include conventional atmospheric processes, astrophysical sources, and potential contributions from decaying dark matter. The parameter space explored involves the dark matter mass and its lifetime, with the assumption that the decay products would produce neutrinos.

Results and Implications

The analysis did not identify any statistically significant excess of neutrino events attributable to dark matter decay, effectively setting new lower bounds on the lifetime of dark matter particles. Specifically, dark matter particles with masses exceeding 10 TeV are constrained to have lifetimes greater than $10^{28}$ seconds at 90% confidence level. These results are the strongest constraints to date derived from neutrino data on dark matter decay models.

Discussion

The constraints improve upon previous limits obtained through gamma-ray, cosmic ray, and cosmic microwave background analyses. Importantly, the results demonstrate the capability of neutrino astronomy, particularly via the IceCube observatory, to limit dark matter models. The lack of a detectable signal suggests that if dark matter contributes to the high-energy neutrino flux, it may be at levels below the current detection threshold or involve non-trivial models beyond simple decay processes.

Future Directions

This research suggests continued observation and analysis with IceCube and similar experiments to further tighten constraints on the dark matter-neutrino connection. Improved detector capabilities and new methodologies could enhance sensitivity to potential weak signals. Moreover, further theoretical developments in dark matter decay models could provide better interpretative frameworks for these experimental results.

Overall, while the data does not reveal a dark matter signature, it enriches the corpus of neutrino astrophysics by placing stringent bounds on dark matter properties, supporting the continued fringe exploration for uncovering potential non-standard physics at high energies.