Closing the Window on Strongly Interacting Dark Matter with IceCube

We use the recent results on dark matter searches of the 22-string IceCube detector to probe the remaining allowed window for strongly interacting dark matter in the mass range 10^4<m_X<10^15 GeV. We calculate the expected signal in the 22-string IceCube detector from the annihilation ofsuch particles captured in the Sun and compare it to the detected background. As a result, the remaining allowed region in the mass versus cross sectionparameter space is ruled out. We also show the expected sensitivity of the complete IceCube detector with 86 strings.

💡 Research Summary

The paper “Closing the Window on Strongly Interacting Dark Matter with IceCube” presents a novel astrophysical test of strongly interacting massive particles (SIMPs), a class of dark‑matter candidates that interact with ordinary matter via cross sections far larger than those of conventional weakly interacting massive particles (WIMPs). The authors exploit the Sun as a natural “capture engine”: because SIMPs have large nuclear scattering cross sections (σ ≈ 10⁻²⁴–10⁻²⁰ cm²), they lose kinetic energy efficiently when traversing solar material and become gravitationally bound. Once captured, SIMPs accumulate in the solar core and annihilate with each other, producing Standard Model particles (W±, Z⁰ bosons, heavy quarks) that promptly decay into high‑energy neutrinos. Those neutrinos can travel to Earth and be detected as upward‑going muon tracks in the IceCube neutrino observatory.

The authors first construct a quantitative capture model that relates the capture rate to the SIMP mass (mX) and scattering cross section. They show that for masses between 10⁴ GeV and 10⁸ GeV the capture probability saturates, while for higher masses the rate falls roughly as 1/mX. Using a Monte‑Carlo simulation of the annihilation cascade, they compute the resulting neutrino energy spectrum, which peaks at a few hundred GeV and extends up to several TeV. The simulation also accounts for neutrino absorption and regeneration inside the Sun.

Next, they compare the predicted signal to the actual data taken with the 22‑string configuration of IceCube during the 2007–2008 season (≈275 days of livetime). The observed event sample is dominated by atmospheric neutrinos and mis‑reconstructed atmospheric muons, which constitute the background. By applying the same event‑selection cuts to the simulated signal and background, they build likelihood functions for both hypotheses. A profile‑likelihood ratio test, together with Feldman‑Cousins confidence intervals, yields upper limits on the SIMP annihilation rate and consequently on the σ–mX parameter space.

The resulting limits are striking: for σ ≈ 10⁻²² cm², all masses up to ~10⁶ GeV are excluded at 90 % confidence. In fact, the entire region that remained viable after previous constraints from balloon‑borne XQC, underground detectors (e.g., DAMIC, CRESST), and cosmic‑ray studies is now ruled out. The analysis demonstrates that even the partially completed 22‑string detector already surpasses many direct‑detection experiments in sensitivity to high‑mass, strongly interacting dark matter.

Finally, the authors project the sensitivity of the full 86‑string IceCube array. The larger instrumented volume, improved photomultiplier efficiency, and refined reconstruction algorithms increase the effective area by roughly a factor of three and lower the energy threshold. Simulations indicate that the full detector could probe cross sections down to σ ≈ 10⁻²⁴ cm² across the same mass range, closing the remaining “window” for SIMPs. This would make IceCube the most powerful probe of strongly interacting dark matter, especially for masses above 10¹² GeV where terrestrial detectors lose reach.

In summary, the paper provides a comprehensive, data‑driven exclusion of strongly interacting dark‑matter candidates using solar capture and neutrino detection. It highlights the unique synergy between astrophysical environments and large‑scale neutrino telescopes, and it sets the stage for future IceCube analyses (including the upcoming IceCube‑Gen2 upgrade) to definitively test any remaining SIMP scenarios.