University of Wisconsin-Madison

Improving dark matter searches with neutrino telescopes

In 2013, the IceCube Collaboration published the world’s best limits on the spin-dependent cross section for weakly interacting dark matter particles. They were derived from the non-observation of annihilation into neutrinos of dark matter gravitationally trapped by the Sun.

Now, the collaboration presents a new likelihood formalism that allows easy integration of any neutrino telescope data into analyses of dark matter theories. In a re-analysis of the 79-string IceCube data, IceCube sets stronger spin-dependent limits and also rules out a number of supersymmetric dark matter models. These results have just been submitted to the Journal of Cosmology and Astroparticle Physics and are accompanied by the release of the associated IceCube data and code, which allows application of the new likelihood formalism to arbitrary dark matter models.

Comparison of our limits with the latest constraints from Super-Kamiokande and PICO. Depending on the annihilation channel, IceCube provides the strongest limits above WIMP masses of ~100-200 GeV. Super-K is more sensitive at the lowest masses. If the annihilation spectrum is soft or heavily suppressed, the PICO experiment provides stronger limits than neutrino telescopes; other direct limits are weaker. Credit: IceCube Collaboration
Comparison of our limits with the latest constraints from Super-Kamiokande and PICO. Depending on the annihilation channel, IceCube provides the strongest limits above WIMP masses of ~100-200 GeV. Super-K is more sensitive at the lowest masses. If the annihilation spectrum is soft or heavily suppressed, the PICO experiment provides stronger limits than neutrino telescopes; other direct limits are weaker. Credit: IceCube Collaboration

High-energy neutrinos from the Sun are great signatures to look for spin-dependent interactions of dark matter with protons. However, the number of theoretical dark matter models, and thus of parameter combinations, is so high that most analyses simplify the searches, assuming that capture and annihilation of dark matter particles have reached equilibrium in the Sun and that dark matter annihilates into a single final state. But this is too strong a simplification. Many models, including supersymmetry, violate these assumptions.

The first search for dark matter annihilation in the Sun using 79-string IceCube data derived limits on single annihilation channels. And ever since then, IceCube researchers have been working on improving the search formalism to be inclusive of all dark matter models. They first developed a formalism for constraining models with annihilation to several final states, like those from theories beyond the Standard Model. In the current study, the formalism is updated to include neutrinos with energies as low as 10 GeV, which results in muons produced at non-negligible angles with respect to the direction of the incoming neutrino. “This will make it fast and easy to use IceCube data to carefully test all sorts of different theories for dark matter,” says Pat Scott of McGill University, one of the corresponding authors of the paper.

Using this formalism, IceCube has analyzed the 79-string data again, resulting in stronger spin-dependent limits on WIMP dark matter, in particular for high WIMP masses. Researchers rule out several supersymmetric models from a very general 25-parameter, weak-scale parameterization of the minimal supersymmetric standard model (MSSM).

+ info “Improved limits on dark matter annihilation in the Sun with the 79-string IceCube detector and implications for supersymmetry,” IceCube Collaboration: M.G.Aartsen et al, Published in the Journal of Cosmology and Astroparticle Physics JCAP04 (2016) 022, dx.doi.org arxiv.org/abs/1601.00653

Data release link and code link

+ info “Search for Dark Matter Annihilations in the Sun with the 79-String IceCube Detector,” IceCube Collaboration: M.G. Aartsen et al, Phys. Rev. Lett. 110, 131302

+ info “Use of event-level neutrino telescope data in global fits for theories of new physics,” P. Scott, C. Savage, J. Edsjö and the IceCube Collaboration: R. Abbasi et al, JCAP 1211 (2012) 057