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Particle physicists to have published results of a decade-long quest, taking us a crucial step closer to understanding where all the antimatter in the universe has gone.
The matter of the universe can be divided into two classes: matter and antimatter, where each particle of matter has an antimatter partner with the same mass and opposite electric charge. But given the similarity between the two, physicists still don’t understand why the universe is dominated by matter. The experiments are working to find places where matter and antimatter behave differently, as part of an ongoing search to understand this mystery. A project called the T2K collaboration in Japan has now released his recommendations. his paper it doesn’tt confirm whether neutrinos differ from antineutrinos, but it gives us some important clues.
“This document represents a very significant step,” Ed Blucher, co-spokesperson for DUNE neutrino University of Chicago experiment that was not involved in this work, he told Gizmodo. “It shows that the experiment has presented enough data to start making important restrictions on this parameter. But it is a significant first step in what is probably a long way to definitely establish whether or not CP symmetry is violated. “By CP symmetry, it means whether neutrinos behave differently than antineutrinos.
If matter and antimatter were exactly the same and followed the laws of physics in exactly the same way, then there would only be photons in the universe, since matter and antimatter annihilate each other by contact. Decades ago, physicist Andrei Sakharov proposed three conditions that a process must meet to explain excess matter over antimatter, or simply why things exist. (plus those conditions later). Perhaps the easiest of the conditions to look for is the violation of CP symmetry, or physical processes that differ between a particle and the mirror image of the same particle (that’s the P, by parity) with the opposite charge (that’s the C, per charge). Basically the CP violation processes are those that work differently between particles and their antiparticles.
Scientists have discovered some violation of the PC in the class of subatomic particles called quarks that form protons and neutrons, but it is still not enough to explain why there is so much more matter in the universe. So they’re also looking for PC violation in leptons, the class of particles that includes electrons and neutrinos. Today, the T2K collaboration in Japan publishes the results of data taken since 2010, looking for evidence of a CP violation process in neutrinos, the most difficult to detect but most abundant particle of matter in the universe. The experiment does not confirm or deny whether neutrinos undergo a CP violation process, but gives scientists hope that an answer will come soon, and shows that probable neutrinos do violate CP symmetry.
T2K consists of a particle accelerator on the east coast of Japan, north of Tokyo, that creates a neutrino beam by colliding protons with a target. This then it creates a beam of other particles that break down into a neutrino flavor called a muon neutrino. This beam passes to a detector that measurements neutrinos, then travels through Earth and is almost 300 kilometers (186 miles) away in a detector called Super-Kamiokande, a tank containing 50,000 tons of water and sensitive tubes to detect water-neutrino interactions. Here, the team measures how many of the neutrinos have changed their taste to electronic neutrinos using a process called neutrino oscillation. The T2K team then changes the accelerator’s magnetic field, creating muonic antineutrinos instead of muon neutrinos, allowing them to search for electronic antineutrinos instead of electrons. neutrinos Finally, they compare the results of the two measurements.
The complex physics and analysis required It means that the result of this experiment is not an easy answer. Instead, the result is an angle measurement, called the CP phase. If the CP phase measures zero, 180, or -180, then the neutrino makes do not violate CP symmetry (i.e. things are equal between the neutrino and tantineutrino). If the angle measures something else, make violate CP symmetrythe laws of physics they differ between neutrinos and their antiparticles. This new study strongly disfavors a wide swath of angles, including zero, but does not rule out 180. It also seems to imply that the best angle to explain the data is around -90, the maximum amount of CP symmetry rape, according to the article published today in Nature. All of this leans towards the conclusion that neutrinos and antineutrinos differ in some very important ways, but again, it is not enough to know for sure.
“This result, for the first time, imposes a strong restriction on the CP phase of leptons by measuring neutrino oscillations, that is, by measuring oscillations from muon neutrino to electron neutrino and antineutrino oscillations from muon to electron antineutrino, “said T2K spokesman Atsuko Ichikawa. Gizmodo
The statistics favor a scenario where neutrinos violate CP symmetry, but experimental data is not yet conclusive. Things are getting closer. Perhaps most importantly, it shows that upcoming experiments like LBNF / DUNE and Super-Kamiokande’s successor, Hyper-Kamiokande, will be able to give a more robust answer in the next decade. These experiments will produce more powerful neutrino beams and combine with more sensitive detectors, allowing scientists to take data and produce results much faster, Federico Sánchez, international co-director of T2K, told Gizmodo. With these projects, researchers will be able to collect in just one year the same amount of data that T2K would collect in 20 years. As is always the case in physics, more data will bring scientists closer to the rigorous statistical threshold required to declare a discovery. Scientists will also need to better model the physical theory of how neutrinos interact with matter and with its detector, Sánchez said.
But even if neutrinos violate the PC, that will not be the end of the story, it is just one of the three conditions of Sakharov to explain the mystery of matter-antimatter asymmetry I mentioned earlier. Scientists must find other processes yet to be discovered, such as the violation of the number of leptons or baryons, essentially, processes where the central numbers that describe neutrinos and protons change in ways yet to be observed, such as the decomposition of protons or neutrinos. annihilating. And even then, theorists must find the correct model in which these deviations actually lead to the differences between matter and antimatter observed in our universe. Observing the violation of the PC in leptons, as well as the violation of the number of leptons, would provide circumstantial evidence that the leptons were to blame for the asymmetry of matter and antimatter of the universe, physics professor Silvia Pascoli of the Durham University in the UK.
And so the search continues and probably will for decades to come. “You have to see this result as a small stone to build a huge building,” Sánchez told Gizmodo. “It is going in the right direction, but it doesn’t uncover the mystery.”
