Search for annihilating dark matter in the Sun with 3 years of IceCube data (1612.05949v2)

Abstract: We present results from an analysis looking for dark matter annihilation in the Sun with the IceCube neutrino telescope. Gravitationally trapped dark matter in the Sun's core can annihilate into Standard Model particles making the Sun a source of GeV neutrinos. IceCube is able to detect neutrinos with energies >100 GeV while its low-energy infill array DeepCore extends this to >10 GeV. This analysis uses data gathered in the austral winters between May 2011 and May 2014, corresponding to 532 days of livetime when the Sun, being below the horizon, is a source of up-going neutrino events, easiest to discriminate against the dominant background of atmospheric muons. The sensitivity is a factor of two to four better than previous searches due to additional statistics and improved analysis methods involving better background rejection and reconstructions. The resultant upper limits on the spin-dependent dark matter-proton scattering cross section reach down to $1.46\times10^{-5}$ pb for a dark matter particle of mass 500 GeV annihilating exclusively into $\tau^{+}\tau^{-}$ particles. These are currently the most stringent limits on the spin-dependent dark matter-proton scattering cross section for WIMP masses above 50 GeV.

Search for Annihilating Dark Matter in the Sun with IceCube Data

This paper presents results from an investigation into the phenomena of dark matter annihilation within the Sun, using data collected over three years by the IceCube neutrino telescope. The central hypothesis posits that dark matter, particularly Weakly Interacting Massive Particles (WIMPs), can be gravitationally trapped in the Sun's core, where they annihilate into Standard Model particles, predominantly producing neutrinos. This potential flux of neutrinos can then be detected by IceCube.

The analysis focused on data accumulated during austral winters from May 2011 to May 2014, a total of 532 days of livetime. During this period, the Sun was beneath the horizon, making it an optimal source of up-going neutrino events distinguishable from the predominant background of atmospheric muons. The paper reports a significant improvement in sensitivity to potential dark matter signals—by a factor of two to four—compared to previous searches, due to enhancements in statistical data and more refined analysis techniques.

Key Findings

1. Sensitivity Improvement: The sensitivity to detecting neutrinos from dark matter annihilation was enhanced, reaching upper limits on spin-dependent dark matter-proton scattering cross sections as low as $1.46 \times 10^{-5}$ pb for a dark matter particle of 500 GeV annihilating exclusively into $W^+W^-$ particles.
2. Search Methodology: The paper employs an unbinned maximum likelihood ratio method to search for statistically significant excesses of neutrino events from the direction of the Sun, which helps differentiate potential dark matter signals from background noise.
3. Results and Interpretation: No significant excess of events indicating dark matter annihilation was observed. Consequently, the paper provides stringent upper limits on the neutrino flux from the Sun, translating into robust constraints on WIMP-proton scattering cross sections.

Implications

• The constraints established are among the most stringent for spin-dependent WIMP interactions at masses greater than approximately 80 GeV, outperforming limits from other neutrino detectors and many direct detection experiments in this range.
• The search can be applied beyond the traditional WIMP hypothesis to any dark matter candidate that scatters off nuclei and produces neutrinos in annihilation processes.
• The findings have broader implications for understanding dark matter distribution and interaction properties, advocating for continued search efforts and cross-validation with other methodologies and experiments.

Future Directions

This research opens pathways for further exploration in both the theoretical and experimental domains. Future studies may build upon these findings by:

• Enhancing detection techniques to improve sensitivity further.
• Extending analyses to broader ranges of dark matter mass and interaction types.
• Integrating results with other observational data to refine models of dark matter distribution and dynamics within the solar core.

Overall, the results presented in this paper contribute important constraints to the paper of dark matter and encourage ongoing efforts to solve one of the most compelling mysteries in contemporary astrophysics.