Sterile neutrinos are potential candidates for dark matter. A repeated anomaly during experiments dedicated to these neutrinos seems to clarify their existence.
” The results are very exciting. At the Los Alamos lab, an intriguing anomaly has been detected during a major experiment. It is relayed in two studies (1, 2) published on June 9, 2022, as well as on the observatory’s website. This anomaly could well be the sign of “sterile neutrinos”, which remain, for the moment, purely hypothetical.
Neutrinos are already, in themselves, ghostly particles. The Universe is full of them, our Sun sends us billions of them every second, but these elementary particles remain very difficult to observe. They have no mass or electric charge. They slip through the densest materials and only interact in the weak nuclear field. To hope to see traces of it, you need observatories like the Super-Kamiokande in Japan – a huge tank of water, several hundred meters underground, with walls strewn with thousands of detectors supposed to detect interactions with water.
As they move, neutrinos oscillate between three “flavors” (a set of physical properties): electronic, muonic, tauic. Except that, in the 1990s, experiments suggested the existence of a fourth flavor, a phase where the neutrinos would not even interact via the weak nuclear interaction. Hence the expression “sterile neutrino”. Their only possible interaction would be with gravity.
“It really reaffirms the anomaly”
The anomaly was detected at the Baksan Neutrino Observatory, located one kilometer underground in the Caucasus Mountains. It mobilizes a source of neutrinos (of “electronic flavor”) and a reservoir of liquid gallium. The reaction between electron neutrinos and gallium produces an isotope, germanium 71. This is what makes it possible to observe the presence of neutrinos in this configuration.
Then the anomaly slips in. The measured rate in germanium-71 production was 20-24% lower than expected based on theoretical modeling. There is a deficit in the number of neutrinos detected: this suggests that there is indeed a sterile flavor of neutrinos. And, what is all the more intriguing, is that this difference was repeated in other similar experiments, further affirming this result.
” This really reaffirms the anomaly we observed in previous experiments. “, explains the chief analyst, Steve Elliott. ” But what this means is not obvious. There are now conflicting results on sterile neutrinos. »
So with sterile neutrinos, we have a ghostly particle, very difficult to observe, which exists in (very) large quantities and which doesn’t interact with anything except gravity… this strangely echoes the very definition of dark matter. Because of this parallel, sterile neutrinos are very strong candidates for this matter, which has never been observed, but appears essential in the standard model of physics.
However, be careful not to jump to hasty conclusions. Other explanations are possible, such as a misunderstanding in the theoretical data of the experiment and the need to review the physics itself “. Even if this other solution were the right one, it would still be just as interesting for fundamental research.
