These studies are designed to explore ethereal particles that store the mysteries of the universe, but according to a new study, 70% of interactions are incorrectly recreated.
If someone took a pen and drew a one-centimeter square on the palm of their hand, this tiny surface area would be crossed by 65 billion neutrinos coming from the Sun’s nuclear processes in a matter of seconds. Every second, another 65 billion people would pass through the little area. Together with light photons, neutrinos are the most prevalent elementary particles in the universe. Despite this, they are elusive and difficult to detect since they have no electrical charge and a mass that is millions of times less than that of an electron.
The scientific community is spending hundreds of millions of euros on devices, such as the Hyper-Kamiokande neutrino observatory in Kamioka, Japan, in an attempt to collect neutrinos and quantify their properties precisely. Some of the universe’s greatest mysteries, according to researchers, are hidden in these ethereal particles. However, on November 24, an international team of scientists disclosed an unpleasant surprise: the models utilized up to that point were riddled with mistakes. They must be fine-tuned in order for us to discover why we exist.
All of the matter and energy in the cosmos began in a place smaller than the full stop at the end of this sentence. Expansion began roughly 13.7 billion years ago with the Big Bang. The theory’s flaw is that at the beginning of the cosmos, the same amount of matter and antimatter — particles with the same mass but opposing electric charge – would have to be created. If such were the case, matter and antimatter would have annihilated each other upon colliding, and the universe as we know it would no longer exist. Antimatter, on the other hand, accounts for less than 0.0000001% of the total matter in the universe. What happened after the Big Bang that allowed matter to triumph over antimatter in its battle?
Many physicists, including Guillermo Megas, a 34-year-old Spaniard, believe the neutrino holds the answer. “Something had to be done to disrupt the cycle.” We have progressed to the point where we are surrounded by matter in our cosmos. “There is no antimatter in a pen or a table,” Megas adds, after spending two years at the University of Tokyo. He goes on to say that the key could be found in a phenomenon known as neutrino oscillation, in which these particles alter their identities as they travel through space and can take on three different sorts, or “lepton flavors” (electron, muon or tau). They are chameleonic, which suggests that, contrary to popular belief, they have mass. Takaaki Kajita and Arthur McDonald were awarded the 2015 Nobel Prize in Physics for their discovery of this phenomena.
The triumph of matter over antimatter
Megas is taking part in the T2K project, an unprecedented attempt to learn more about this transformation. Scientists working on the project created a beam of neutrinos near Tokai, Japan’s eastern shore, and transported it to Kamioka, 295 kilometers to the west, in the hopes of capturing them at the Super-Kamiokande, a subterranean detector built inside an ancient zinc mine in 1996. Trillions of neutrinos pass through it unnoticed, but some do smash with the material of a massive tank that stands 41 meters tall and holds 50,000 tons of water. Scientists can deduce the neutrinos’ unknown features by observing variations in their composition and intensity as they travel.
However, these measurements are based on theoretical models that anticipate how neutrinos will interact with atom nuclei. The simulations that use these models are beset with imprecisions, according to a new study published in the science journal Nature on November 24. These must be fine-tuned, especially now that massive new detectors are being built, such as the Hyper-Kamiokande, which is eight times larger than the Super-Kamiokande and will cost over €500 million, and the US-based DUNE, a similar project based in a former gold mine in South Dakota and valued at over €900 million.
Neutrinos have very little interaction with matter. They can even pass through a nine-billion-kilometer-thick lead barrier. Scientists can only detect a single neutrino among the thousands of billions created in particle accelerators in current experiments like the Japanese T2K or the US NOvA. When neutrinos interact with matter, such as when they collide with atomic nuclei in water at the Super-Kamiokande facility, they produce three types of particles, depending on the neutrino’s flavor: the electron, muon (which are 200 times heavier than electrons), and tau (which are 4,000 times heavier).
Experiments are currently underway to measure these easily detectable resulting particles in order to compute the parameters of neutrino oscillations in an attempt to reconstitute the energy contained in the theoretical models’ processes. The authors of the new study, lead by Israeli MIT physicist Or Hen, replicated previous tests by substituting electrons with neutrinos, a particle that scientists have complete control over. The findings are both unexpected and alarming. According to Megas, a co-author of the study, the data reveals that 70 percent of the interactions are poorly reproduced by existing simulations. If the models are corrected, it will be possible to determine whether neutrino oscillation led matter to triumph over antimatter after the Big Bang.
Physicist Pilar Coloma emphasizes the need to enhance the models, particularly in future DUNE and Hyper-Kamiokande experiments that aim to quantify neutrino properties with hitherto inconceivable rigor. “To achieve this degree of precision, systematic errors must be entirely under control,” explains Coloma of the Madrid Institute of Theoretical Physics.
The Hyper-Kamiokande could potentially pave the way for a new type of particle physics, one that goes beyond the Standard Model, a theory that has been in development since the 1970s and defines the world using 17 fundamental particles – nature’s building blocks – and their interactions. “Another property or perhaps a neutrino that we don’t know about could be discovered,” adds Coloma, who is also a co-author of the new study.
Several laboratories have tried unsuccessfully over the last few years to locate evidence of a potential fourth neutrino, termed “sterile” due to its inability to interact with the other known particles. Sterile neutrinos are one of the probable components of dark matter, the enigmatic particles that are considered to make up 85 percent of all matter in the universe, five times more than classical matter, the stuff that provides life to everything from stars to humans. “Physics beyond the Standard Model must exist,” Coloma argues. “The million-dollar issue is whether we’ll find it in the next several years.”