One of modern cosmology’s most perplexing mysteries is dark matter. On one hand, the standard model of particle physics does not contain any particles that could account for dark matter, and we have not been able to detect its effect locally. On the other hand, astronomers have gathered a wealth of supporting evidence through galaxy clustering statistics, gravitational lensing, and fluctuations in the cosmic microwave background. We just can’t seem to completely explain this sound theory. That typically indicates that dark matter can either be confirmed or disproved with the next scientific discovery. The good news is that there are numerous initiatives looking for dark matter, and one of them, the IceCube Neutrino Observatory, recently announced a new finding.
Although IceCube is primarily a neutrino observatory, it can also detect local impacts of dark matter that result in neutrinos. According to a popular scenario, dark matter particles are made up of large particles that largely interact with one another and only weakly with ordinary matter particles. These WIMPs, or weakly interacting massive particles, may be present in the Earth’s core.
If the WIMP model is correct, when dark matter strikes a huge object like a planet or star, collisions with dense ordinary matter should cause it to slow down, trapping some WIMPs gravitationally inside the body. Periodically, these WIMPs would collide with one another, resulting in neutrino-producing particle decays. This implies that IceCube should be able to detect an excess of neutrinos coming from the center of the Earth.
In this study, the team examined ten years’ worth of IceCube data and discovered no proof of an excess of neutrinos. This basically excludes WIMPs with a mass more than 100 GeV, or a little bit more than 100 proton masses, given the energy cross-section of IceCube detectors. This outcome is consistent with those of other investigations that also rule out high-mass WIMPs. Although it is still feasible for lower mass dark matter particles, we have a long history of excluding these possibilities.
In order to improve IceCube’s sensitivity, more dark matter tests seeking for WIMPs with lower masses will be possible. We may now be able to find dark matter close to home thanks to this, but time is running out. We may need to consider alternatives like modified gravity since we have already ruled out a number of potential sources of dark matter. That, however, is a tale for another time.