Many experiments that have studied neutrinos since the 1990s found something really strange: too many particles were visible on the detectors. In particle physics, even small deviations from expected experimental results excite scientists. Now, a new experiment conducted more than two kilometers deep underground from Russia’s Caucasus Mountains has confirmed a previously observed anomaly, pointing to an as-yet-unconfirmed new elementary particle called a ‘sterile neutrino’. It is either that or our physics is flawed, so these results are incredibly consequential, regardless of the outcome.
sterile neutrinos deep underground
Neutrinos are the most abundant particles in nature, perhaps second only to photons, particles of light. 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 originate in the upper atmosphere when gases collide with cosmic rays from supernovae and other events in space.
There are three known types or flavors of neutrinos: electron, muon, and tau neutrino. But many scientists believe there is a fourth taste in the shadow, waiting for its rightful place with its mite family. Temporarily called sterile neutrinos, if they exist, they could help solve some longstanding mysteries in physics, such as why neutrinos have mass when, in theory, they should be massless like photons. needed. Sterile neutrinos – so named because they are supposed to interact with other particles entirely through gravity, while the other three tastes also do so through the weak force – the nature of dark matter, of the invisible and elusive matter can explain, which accounted for 85%. All matter in the universe, even though we cannot measure it directly.
Researchers affiliated with the Bachson Experiment on Sterile Transition (BEST), including US researchers at Los Alamos National Laboratory, used an irradiated disk of chromium 51 (a synthetic radioisotope of chromium) and a powerful source of electron neutrinos for internal and external radiation. used. Parts of a tank made of gallium. As a result of this reaction, the experiment produced the isotope germanium 71.
This was completely expected, but the discrepancy was that the production rate was 20-24% lower than the theory suggested. The methodology of the experiment is assumed to be flawless, and, furthermore, the discrepancy is in the same ballpark registered by other previous experiments.
“The results are very exciting,” said Steve Elliott, principal analyst on one of the teams evaluating the data and a member of the Los Alamos Department of Physics. “This certainly confirms the discrepancy observed in previous experiments. But what this means is unclear. There are now conflicting results regarding sterile neutrinos. If the results indicate that fundamental nuclear or nuclear physics are wrong If understood, it will also be very interesting.”
One of the earlier experiments that had similar results was the forerunner of Best, a 1980s solar neutrino experiment called the Soviet-American Gallium Experiment (SAGE), which also used gallium and a high-intensity neutrino source. was used. Both BEST and SAGE were carried out thousands of meters below the entrance of a tunnel at the Buxon Neutrino Observatory, located in the Buxon River Gorge in Russia’s Caucasus Mountains.
Neutrino detectors are usually buried deep underground to protect them from interference from cosmic rays and other radiations that can wreak havoc on experiments if detectors are exposed to the surface. The next generation neutrino detector, called the Deep Underground Neutrino Experiment, or DUNE, is currently being built 48 kilometers (30 miles) below the ground at the Fermi National Accelerator Laboratory in Batavia, Illinois. When completed, it will be able to shoot beams of neutrinos through Earth’s mantle.
Did we miss out on dark matter because our understanding of physics is flawed?
There are many reasons why physicists love neutrinos. They provide a direct connection between us and the Sun’s center, allowing scientists to look inside nuclear fusion processes without having to place detectors in space. But perhaps the most interesting thing about neutrinos is that they oscillate between tastes, just as a chameleon changes color in response to its surroundings. A particle that starts out as an electron neutrino, for example, can transform into a tau or muon neutrino, and vice versa.
The lag in the timing of these oscillations, as recorded by the experiment in Russia, and others similar before it, suggest that there is a fourth taste that we are missing. This hypothetical particle may also be an important component of dark matter.
But this is not to say that a fourth type of elementary particle is the only explanation. The results of the experiment also raise the interesting possibility that our current theoretical framework for describing neutrinos is flawed. That wouldn’t be bad news at all. Science is a constant work in progress in which the status quo is always accompanied by new, compelling evidence. In the process, the institution of science becomes stronger and more reliable, as well as better equipped to answer increasingly complex questions about nature.
appeared in the conclusion physical review paper,