Credit: Pixabay.
Several experiments conducted since the 1990s studying neutrinos found something really strange: there were too many particles appearing in the detectors. In particle physics, even small deviations from the expected experimental results have excited scientists. Now, a new experiment conducted deep underground, more than two kilometers below the Caucasus mountains of Russia, has confirmed the anomaly seen above, pointing to a new as yet unconfirmed elementary particle called “sterile neutrino.” Is that it or our physique is flawed, so these results are incredibly consistent, regardless of the result.
Sterile neutrinos deep underground
Neutrinos are the most abundant particles in nature, perhaps just behind photons, light particles. You may not notice them, but they are everywhere. In fact, every second, about a trillion neutrinos pass through your hand. Most of them originate from the sun, while others are generated in the upper atmosphere when gases are impacted by the cosmic rays of supernovae and other events in space.
There are three known types or flavors of neutrinos: electron neutrinos, muons, and tau. But many scientists believe that there is a fourth flavor that persists in the shadows, waiting for its rightful place with its particle family. Temporarily called sterile neutrinos, if they exist, could help solve many persistent mysteries in physics, such as why neutrinos have too much when, in theory, they should be without mass like photons. Sterile neutrinos, so named because they are supposed to interact with other particles only through gravity, while the other three flavors are also supposed to interact with a weak force, can also explain the nature of dark matter, invisible and elusive matter. which represents 85% of all matter in the universe, although we cannot measure it directly.
Located underground at the Baksan Neutrino Observatory in the Caucasus Mountains in Russia, the completed two-zone gallium target, on the left, contains an inner and outer gallium tank, which is irradiated. by a source of electronic neutrinos. Credit: AA Shikhin
Researchers affiliated with the Baksan Experiment on Sterile Transitions (BEST), which includes U.S. researchers at the Los Alamos National Laboratory, used irradiated chromium 51 disks (a synthetic chromium radioisotope) and a powerful source of electronic neutrinos to irradiate ‘inside and outside. parts of a deposit made of gallium. As a result of this reaction, the experiment produced the isotope germanium 71.
This was fully expected, but what was abnormal was that the production rate was 20-24% lower than the theory suggested. The methodology of the experiment is believed to be flawless, and in addition, the discrepancy is at the same stage as other previous experiments.
“The results are very exciting,” said Steve Elliott, chief analyst for one of the teams evaluating the data and a member of the Los Alamos physics division. “This definitely reaffirms the anomaly we saw in previous experiments. But what this means is not obvious. There are now contradictory results on sterile neutrinos. If the results indicate that fundamental nuclear or atomic physics is misunderstood, that too It would be very interesting. “
One of the previous experiments with similar results was the precursor to BEST, a 1980s solar neutrino experiment called the Soviet-American Gallium Experiment (SAGE), which also used gallium and a neutrino source. high intensity. Both BEST and SAGE were made thousands of meters below the entrance of a tunnel to the Baksan Neutrino Observatory, located in the Baksan River Gorge in the Caucasus Mountains of Russia.
Neutrino detectors are usually buried deep underground to protect them from interference from cosmic rays and other radiation that would wreak havoc on the experiment if the detectors were exposed to the surface. A next-generation neutrino detector called the Deep Underground Neutrino Experiment, or DUNE, is currently being built 48 kilometers (30 miles) underground at Fermi National Accelerator Laboratory in Batavia, Illinois. When complete, it will be able to fire neutrino beams through the Earth’s mantle.
Have we lost the dark matter because our understanding of physics is flawed?
There are many reasons why physicists love neutrinos. They provide a direct link between us and the sun’s core, allowing scientists to look inside nuclear fusion processes without having to place detectors in space. But perhaps the most intriguing thing about neutrinos is that they oscillate between flavors, like a chameleon changing color in response to its surroundings. A particle that begins as an electron neutrino, for example, can become a tau or muonic neutrino, and vice versa.
The gaps in time of these oscillations recorded by the experiment in Russia, and other similar ones above, suggest that we lack a fourth flavor. This hypothetical particle can also be an important component of dark matter.
But this does not mean that a fourth type of elementary particle is the only explanation. The results of the experiment also raise the intriguing possibility that our current theoretical framework describing neutrinos is flawed. That wouldn’t be bad news at all. Science is a constantly evolving work in which the status quo is always added to new and compelling evidence. In the process, the institution of science becomes stronger and more credible, as well as better equipped to answer increasingly complex questions about nature.
The findings appeared in Physical Review Letters.