No, things are not looking good at the moment for the WIMPs, those hypothetical particles that were once considered promising candidates for dark matter. It is true that a team of researchers has been trying to prove it for years with the help of the DAMA experiment in the Gran Sasso National Laboratory. However, the international research community has always been skeptical – and this skepticism is probably right. Because a study published in the journal "Science Advances" suggests the conclusion: whatever the DAMA experiment proves, WIMPs are probably not.
On the one hand, this is a shame, because it means that researchers still have no idea what the dark matter is made of. The majority of all matter in the universe should form, have significantly influenced the structural formation in the cosmos and still maintain our galaxies from it. Tragic that the dark matter is probably only noticeable by gravity - and otherwise does not interact until the most, at most, with the remaining, visible matter.
On the other hand, the findings of the research group led by Govinda Adhikari from the University of California San Diego are a good example of how science actually works. While the DAMA collaboration has been claiming for years that it has definitely found signs of WIMPs, it is quite reluctant to share its raw data with experts. Other dark matter detectors, which are also searching for the WIMPs, have not found any such signs. However, some of these detectors work with other materials to detect the interactions of the WIMPs with the atoms of the noble gas xenon, for example. DAMA, on the other hand, uses special sodium iodide crystals.
Cosine checks Damas dark matter
In order to test the DAMA results really independently, a detector had to be found that works with the same crystals. And one of these is in South Korea and is called COSINE. It was specifically built to either confirm – or refute – DAMA results. In 2018, the researchers involved came to the conclusion: COSINE cannot reproduce the DAMA signal after almost 60 days of observation.
However, this was only true for a variety of WIMPS. As long as a particle is only hypothetical, it can have all possible properties. Maybe it's a little more or a little less massive pond? Perhaps the dark matter in the Milky Way is distributed differently than the current model ideas explained? And maybe the South Korean detector still reacts differently than the Italian variant? So there were still a few options to reconcile the measurements of the Dama collaboration in Italy and the measurements of the Cosine 100 experiment.
The team led by Govinda Adhikari analyzed data from 1.7 years of COSINE-100. The conclusion is clear: they found no evidence that any existing WIMPs had interacted with the detector during this period. However, in order to finally refute the DAMA signal, COSINE-100 must now collect data for more years, explains the research group led by Adhikari. The final verdict is thus postponed for some time.
