Superheavy dark matter and IceCube neutrino signals: Bounds on decaying dark matter

Superheavy dark matter may show its presence in high-energy neutrino signals detected on Earth. From the latest results of IceCube, we could set the strongest lower bound on the lifetime of dark matter beyond 100 TeV around ${10}^{28}s$. The excess around a PeV is noticed and may be interpreted as the first signal of dark matter even though further confirmation and dedicated searches are invited.

Figure 1

Neutrino survival probability due to Earth absorption at the South Pole near the surface location as function of the neutrino energy for an isotropic flux compared to the flux expected from dark matter decay originating from a NFW halo distribution and parametrized as Ref. [28]. The effect of the Glashow resonance at 6.3 PeV for antielectron neutrinos becomes small as we have averaged overall neutrinos flavors. Detailed treatments can be found elsewhere [30].

Figure 2

Derived limit using the high-energy neutrino flux observed by IceCube in comparison to the previous experimental constraints from IceCube, Fermi-LAT, and PAMELA and derived limits from neutrino data [24]. Excluded are regions below the pictured lines. The decay $\chi \to \nu x$ includes $\nu Z$ and $\nu H$ channels thanks to the Goldstone equivalence theorem.