Searching for dark matter with neutrinos

As the Solar System moves through the halo of the Milky Way, WIMPs become swept up by the Sun. Although dark matter particles interact only weakly, they occasionally scatter elastically with nuclei in the Sun and lose enough momentum to become gravitationally bound. Over the lifetime of the Sun, a sufficient density of WIMPs can accumulate in its centre so that an equilibrium is established between their capture and annihilation rates. The annihilation products of these WIMPs include neutrinos, which escape the Sun with minimal absorption, and thus potentially constitute an indirect signature of dark matter. Such neutrinos can be generated through the decays of heavy quarks, gauge bosons and other products of WIMP annihilation, and then proceed to travel to Earth where they can be efficiently identified using large volume neutrino detectors.

Compared with other dark matter detection techniques, indirect dark matter searches using neutrinos involve minimal astrophysical uncertainties. Although the capture rate of WIMPs onto the Sun depends on the local density and velocity distribution of dark matter (as do direct detection rates), the rate at which WIMPs annihilate is determined by the total number of WIMPs in the core of the Sun, which have accumulated over billions of years. As a consequence, any structure or other variations in the local dark matter density (subhaloes, streams, etc.) become averaged out.