Neutrinos in IceCube/KM3NeT as probes of Dark Matter Substructures in Galaxy Clusters

TL;DR

This paper forecasts the sensitivity of IceCube and KM3NeT neutrino detectors to dark matter annihilation signals in galaxy clusters, highlighting the impact of substructures and potential improvements at lower dark matter masses.

Contribution

It introduces a detailed sensitivity forecast for neutrino detection of dark matter in galaxy clusters, emphasizing the role of substructures and proposing a low-energy extension for better low-mass dark matter detection.

Findings

Sensitivity to heavy dark matter annihilation cross section is around 10^{-24} cm^3 s^{-1}.

Dark matter substructures can enhance signals by 2-3 orders of magnitude.

Lower dark matter masses could be better probed with improved cascade reconstruction and low-energy extensions.

Abstract

Galaxy clusters are one of the most promising candidate sites for dark matter annihilation. We focus on dark matter with mass in the range 10 GeV - 100 TeV annihilating to muon pairs, neutrino pairs, top pairs, or two neutrino pairs, and forecast the expected sensitivity to the annihilation cross section into these channels by observing galaxy clusters at IceCube/KM3NeT. Optimistically, the presence of dark matter substructures in galaxy clusters is predicted to enhance the signal by 2-3 orders of magnitude over the contribution from the smooth component of the dark matter distribution. Optimizing for the angular size of the region of interest for galaxy clusters, the sensitivity to the annihilation cross section of heavy DM with mass in the range 300 GeV - 100 TeV will be of the order of 10^{-24} cm^3 s^{-1}, for full IceCube/KM3NeT live time of 10 years, which is about one order of magnitude better than the best limit that can be obtained by observing the Milky Way halo. We find that neutrinos from cosmic ray interactions in the galaxy cluster, in addition to the atmospheric neutrinos, are a source of background. We show that significant improvement in the experimental sensitivity can be achieved for lower DM masses in the range 10 GeV - 300 GeV if neutrino-induced cascades can be reconstructed to approximately 5 degrees accuracy, as may be possible in KM3NeT. We therefore propose that a low-energy extension "KM3NeT-Core", similar to DeepCore in IceCube, be considered for an extended reach at low DM masses.