This underground device, which will be in operation in 2022 or 2023, will answer a series of basic questions by detecting neutrinos from various sources: who is the bigger and who is the smaller of the three known neutrinos? What is the total mass of neutrinos in the universe and how do they affect the formation of the universe and the distribution of galaxies? How much chemical energy in the earth’s interior drives the earth’s movement? Electron neutrinos and μ neutrinos in cosmic rays can be converted to tau neutrinos. Image source: icecube / NASA < / P > < p > neutrinos are a wonderful family of subatomic particles. They’re everywhere, pouring in from the sun, deep space, and earth, flying through our bodies, trillions per second. These particles are so small that they rarely interact with anything, making them extremely elusive and difficult to study. In addition, neutrinos have different types, or flavors, that travel at close to the speed of light, and can switch from one type to another in flight. Scientists believe that these strange behaviors may provide insights into the history of the universe and the future of physics. < / P > < p > after nearly six years of excavation, about 150 km west of Hong Kong, a huge neutrino laboratory is taking shape in the rolling hills. Jiangmen neutrino experiment (Juno) will become one of the most powerful neutrino experiments in the world, which is as famous as the “top Shengang” experiment (hyper-k) in Japan and “dune neutrino experiment” (dune) in the United States. Using two nearby nuclear power plants as neutrino sources, the goal of Jiangmen experiment is to learn more about these particles, so as to answer a basic question: which is the mass of the three known neutrinos? Although the researchers know the particles have tiny masses, they don’t know their exact size. The existing evidence shows that the neutrino mass of two of them is close, and the third is different. But scientists don’t know whether the third type is heavier or lighter than the other two. The former is called “positive mass order” and the latter is called “inverse mass order”. Joseph Lykken, a theoretical physicist at Fermi National Accelerator Laboratory, said neutrino mass order is a key parameter that researchers need to determine. “In fact, many other questions depend on the answer to this question.” He added. For example, the answer could help scientists better estimate the total mass of neutrinos in the universe and determine how they affect the formation of the universe and the distribution of galaxies. Although neutrinos are the lightest of all known matter particles, there are so many neutrinos in the universe that they must have had a great influence on the distribution of ordinary matter. Understanding the mass order of neutrinos can also help explain why neutrinos have mass, a phenomenon that contradicts earlier expectations. Jiangmen neutrino experiment was proposed in 2008, and now there are more than 650 scientists working for it, nearly half of them are from outside China. By the end of this year or early 2021, researchers will begin assembling 13 story spherical detectors. The detector will be covered with 43000 photocells for detecting light and filled with 20000 tons of specially prepared liquid. At 700 meters below the ground, electronic anti neutrinos (the type of neutrinos produced by nuclear reactors) collide with protons with very little probability, triggering reactions in the liquid, producing two flashes of light less than a millisecond apart. “This little coincidence is seen as a nuclear neutrino signal,” said Juan Pedro Ochoa ricoux, a particle physicist at the University of California, Irvine He is the co leader of one of the two photomultiplier systems in Jiangmen experiment. When neutrinos arrive at the detector from a nuclear power plant tens of kilometers away, only about 30% of them will remain their original identity, and the rest will be converted into other types. According to Cao Jun, deputy spokesman for the Jiangmen neutrino experiment and from the Institute of high energy physics, Chinese Academy of Sciences, which is the lead agency of the project, the observation station will be able to measure this ratio very accurately. After the start of operation, Jiangmen experiment is expected to see about 60 such signals every day. However, to make a convincing statistical answer to the question of mass order, scientists need 100000 signals – which means the experiment has to run for years to get an answer. At the same time, Jiangmen experiment will detect and study neutrinos from other sources, including 10 to 1000 neutrinos from the sun every day, and thousands of neutrinos that suddenly emerge when a supernova explodes at a certain distance from earth. The Jiangmen neutrino experiment can also capture the so-called earth neutrinos produced by the natural decay of radioactive elements such as uranium 238 and thorium 232. So far, studying the earth’s neutrinos is the only effective way to understand how much chemical energy in the earth’s interior drives our planet, said William McDonough, a geologist at the University of Maryland, who has been involved in the Jiangmen experiment since the beginning of the experiment. “Jiangmen experiment is a game changer in this respect.” He said. All the existing detectors in Japan, Europe and Canada can see about 20 neutrinos a year, while the Jiangmen experiment will detect more than 400 neutrinos a year in the future. Wang Yifang, spokesman for the Jiangmen neutrino experiment and director of the Institute of high energy, said the experiment is now dealing with the problem of underground water seepage, which has delayed the construction progress for two years. Engineers still need to pump 12000 tons of groundwater a day, but the water level has dropped significantly. Flooding is not uncommon in the construction of underground laboratories, as has the Sudbury Neutrino Observatory (SnO) in Ontario, Canada. Wang Yifang believes that this problem will be solved before the construction is completed. Wang Yifang said that the Jiangmen experiment should start at the end of 2022 or early 2023. By the end of the 1920s, the dune neutrino experiment in the United States and the top shenoka experiment in Japan will also join the ranks. Using the neutrinos produced by the accelerator, the dune experiment will be able to measure the neutrino mass order with the highest accuracy. It will also study a key parameter called CP violation, a physical measure of the difference between neutrinos and their antiparticle behavior, which can reveal whether neutrinos are part of the reason why the universe is mainly composed of positive matter. “The results of Jiangmen experiment on neutrino mass order will help sand dune experiment to find and measure CP damage most effectively.” Said likan. Earlier experiments, as well as other neutrino observatories being built, may also reveal something that scientists did not expect. The history of neutrino research shows that these particles often behave unexpectedly, and liken added, “I think it’s a surprise to combine these experimental results.” Privacy Policy