The nature of dark matter—roughly 85% of all matter in the universe—is one of the most important unresolved questions in modern physics. Thus far, no experiment has been able to determine what dark matter is made of.
A possible candidate for dark matter are the hypothesized weakly interacting massive particles (WIMPs), which hardly interact with other particles. These WIMPs can get gravitationally trapped inside celestial bodies such as the Earth and then forced into very close proximity to other WIMPs. Such close encounters can lead to a process known as self-annihilation where the WIMPs collide with each other and disintegrate into other particles.
Among those, only the elusive neutrinos are able to escape the Earth’s dense core and reach the surface where the IceCube Neutrino Observatory can detect them.
In a study recently submitted to The European Physical Journal, the IceCube Collaboration presents results from a search for dark matter using neutrinos. No significant excess of a dark matter signature was found coming from the center of the Earth, but upper limits were set on the strength of the interaction of dark matter with standard model particles.
For the search, researchers used 10 years of IceCube data and focused on muon neutrinos that escaped from the center of the Earth and left a track-like (straight path) signature inside the detector. They looked for an excess of neutrinos coming from the Earth as a result of dark matter self-annihilation, with masses ranging from 10 GeV to 10 TeV.
“We were able to set limits on how strong dark matter can interact with standard model particles,” says Juanan Aguilar, a professor at the Université Libre de Bruxelles and colead on the study. ”These limits are competitive with direct detection experiments of dark matter.”
With the completion of the currently ongoing IceCube Upgrade project, which will install seven more strings of sensors in the next few years, IceCube will have increased sensitivity to lower energies and, thereby, increased sensitivity to low-mass dark matter.
“In doing the analysis we identified opportunities to improve future dark matter studies using more data that includes all neutrino types,” says Giovanni Renzi, who coled the study while a PhD student at the Université Libre de Bruxelles. “We would basically be harnessing the full potential of IceCube to detect neutrinos and, in turn, dark matter.”
+ info “Search for dark matter from the center of the Earth with ten years of IceCube data,” IceCube Collaboration: R. Abbasi et al. Submitted to The European Physical Journal. arxiv.org/abs/2412.12972