In a 4,000-meter-long laboratory facility more than a mile below the Caucasus mountains in Russia, an experiment with nearly two dozen metal disks composed of a rare radioisotope has revealed an anomaly that could reshape our understanding of physics.
While the above description may seem to come from a scene in The X Files, what it actually describes is the setting for a recent experiment to confirm the possible existence of a new elementary particle: sterile neutrinos.
The Baksan Neutrino Observatory is arguably one of the most unusual laboratories in the world. It exists below the Baksan River Gorge in the Russian Caucasus, construction began in 1977, and today is home to an extensive network of underground facilities that house an arsenal of technological wonders, including the Telescope of Baksan underground sparkle (BUST).
Since 2019, the location has also been the site of the Baksan Sterile Transition (BEST) experiment, a study being conducted inside a 4,000-meter-long horizontal tunnel that passes below the slopes of the Mount Andyrchi. An extension of the tests that began in the 1980s as a joint research effort between the Soviets and the United States to measure the flow of solar neutrinos, BEST researchers have spent several years working toward new ideas in physics. which can even help illuminate dark matter, one of the greatest persistent mysteries in the universe.
Now, according to a new scientific paper describing the results of the ongoing experiment, confirmation of an anomaly that has long puzzled physicists could mean that science is nearing confirmation of the existence of sterile neutrinos. . This, or it may point to the possibility that something might be wrong with our current understanding of the standard model of physics.
“The results are very exciting,” said Steve Elliott, senior analyst in the Physics Division at Los Alamos National Laboratory, which is working with the BEST experiment.
“This definitely reaffirms the anomaly we’ve seen in previous experiments,” Elliot said in a statement released by the Los Alamos National Laboratory. “But what that means is not obvious.”
At the heart of the mystery is the sterile neutrino, a still hypothetical particle that physicists recognize as unique, if it exists, due to the way its interactions are only related to gravity, unlike other types of interactions. recognized within the standard. model.
Neutrinos are currently known to exist in three types: the electron, the muon, and the tau. Previous experiments conducted at 2007 at the Fermi National Accelerator Laboratory in Batavia, Illinois, failed to locate tests of a fourth variety of neutrons. However, the results of the new BEST study may have shaken the foundations of the standard model again, so it revives the questions that persist about our understanding of physics.
“There are now conflicting results on sterile neutrinos,” says Elliot. “If the results indicate that fundamental nuclear or atomic physics is misunderstood, that would also be very interesting.”
In a recent study, BEST researchers found that production rates for a particular isotope, germanium 71, were almost 25% lower than expected in the standard model. Germanium 71 was produced with the help of a set of 26 disks made of another isotope — chromium 51 — that served as a point of reaction between electron neutrinos and gallium.
The two-zone gallium target used in the recent experiment, which is irradiated by a source of electronic neutrinos (Credit: AA Shikhin).
This is significant because it aligns in terms of past observations of the anomaly that researchers first detected in previous experiments that began in the 1980s. The Soviet-American gallium experiment, or SAGE, had also conducted tests with gall and neutrino sources known to be high intensity. The SAGE experiments had been the first to notice the so-called “rooster anomaly” recognized again during the recent BEST experiments.
Although there is more than one possible explanation for the anomaly, the oscillation of electron neutrino particles in their hypothetical sterile neutrino states is one of the interpretations that researchers have considered. If this were shown to be the cause of gallium deficiency in both experiments, it would be important for sterile neutrinos to be a component of the mysterious dark matter believed to exist throughout the universe, parts of which may be in weakly interacting particles.
However, it is still possible that there are other interpretations that may better explain the anomaly. Elliot and Los Alamos researchers reviewing the BEST results have found that some information that researchers do not currently have involves cross-sectional measurements of electron neutrinos at energies comparable to those in the BEST and SAGE experiments. One possible way to achieve these measurements could include unraveling another enigma in physics: the density of temperamental electrons within the atomic nucleus, which has been proposed as a possible input for measuring the cross section of electron neutrinos.
To help limit the possibility of error, much attention was paid to the use of counting systems, as well as to the sources of radiation, their placement, and other elements of the experiment. However, given the possibility that certain theoretical contributions may remain in question, it can still be shown that there are aspects of physics in operation in the experiments that will need to be rethought.
Looking to the future, BEST may attempt to replicate the experiment with minor changes that include a different source of radiation, capable of producing shorter oscillation wavelengths depending on its decay rate of half-life.
If the same observations of “false” electronic neutrinos occur in future experiments, unlike the predicted results according to the standard model of physics, it may in fact point to the reality of the sterile neutrino sought for a long time and therefore an understanding. deeper than the subtle mechanics of our universe.