The race to decode ghost particles between the US and China

In a granite cave deep beneath the hills of southern China, workers will soon complete a 600-ton sphere that could explain some of the greatest mysteries of modern physics. The thermoplastic plexiglass sphere is the heart of the Jiangmen Underground Neutrino Observatory (JUNO), a $300 million facility designed to measure neutrinos, the smallest subatomic particles ever seen by physicists. know, follow NBC.

Sometimes called “ghost particles,” neutrinos are invisible, nearly massless, and move at nearly the speed of light. They include three types, the largest of which is estimated to be one millionth of the mass of an electron. Neutrinos can fly through Earth and other matter without interacting. That’s why they are so mysterious to the physicists. Learning about neutrinos will help decipher the puzzling imbalances of the Big Bang theory. According to the standard model of physics, that event should have produced equal amounts of matter and antimatter. But the material is much more abundant and scientists still don’t know why.

The goal of JUNO and many other neutrino observatories scheduled to operate in the coming years is to measure differences in neutrino masses. Because the grain is so small, it’s very difficult to do it accurately. JUNO is built at a depth of 700 m below the ground, thus protecting the neutrino particles under study from the impact of cosmic rays. To reach the observatory sphere, it is necessary to travel by cable car at a speed of about 6.4 km/h along a long tunnel sloping into a granite cave. Before operations begin next year, the sphere and the underground area around it will be sealed and filled with liquid.

The cable car runs down to the Juno station sphere in about 15 minutes. At the end of the tunnel, visitors are given hard hats and completely white jumpsuits along with rubber boots. Then, each person passes through the disinfection chamber. Inside the cave where the sphere is located, workers carrying flashlights climbed up railings and beams to clean up dirt.

Trillions of neutrinos pass through the human body every second. The Sun creates them through thermonuclear reactions, and so do nuclear power plants. Some come from supernova explosions in space. Neutrinos form pairs with anti-neutrinos. JUNO is designed to collect antineutrinos emitted from two nuclear power plants 53.1 km from the observatory. JUNO’s 13-story-high sphere is filled with a special liquid called scintillator, immersed in a tank of pure water, according to Wang Yifang, project leader and director of the Central Institute of High Energy Physics. Quoc.

When antineutrinos come into contact with liquid, they trigger a chemical process that creates a flash of light that can be captured by sensors covering the sphere. According to Wang, the flash lasts only about 5 nanoseconds, so the researchers hope to record about 60 such events per day using thousands of photomultiplier lights around the sphere. With that approach, JUNO can measure differences in antineutrino masses 10 times better than previous devices.

JUNO is part of China’s ambition to become a scientific power. This will be the first of three new generation neutrino observatories to open in the next 10 years. In Japan, the Hyper – Kamiokande observatory is scheduled to operate in 2027. An American program called the Deep Underground Neutrino Experiment (DUNE) will include a particle accelerator that transmits neutrino beams underground from Illinois to South Dakota, starting in 2031. The three observatories all plan to use different technologies to detect ghost particles, so they can complement and compete with each other.

The team of experts at Fermilab wanted to study neutrinos in unprecedented detail with DUNE. That’s why DUNE will have the largest neutrino detectors ever built. Once completed, the experiment will begin with a series of particle accelerators at Fermilab’s facility outside Chicago, Illinois. The accelerators will shoot a powerful beam of neutrinos through detectors at Fermilab. The particle beam will then travel underground 1,287 km to the detector at the Sanford South Dakota Underground Research Facility.

Tracking how neutrinos change over such long distances between Illinois and South Dakota will help scientists better understand the oscillations. Conducting the experiment at a depth of 1.6 km underground protects the fragile vibrating particles from the energetic cosmic rays that continuously bounce off the Earth’s surface every second, threatening to affect the data.

Scientists hope to answer three main questions with DUNE: why the universe is made of matter instead of antimatter, what happens when a star collapses, and whether protons decay. DUNE’s particle beam is designed to produce both neutrinos and antineutrinos. Observing fluctuations in each type can help researchers guess what happens to all antimatter.

Wang wants JUNO to win the race with the United States and other countries to determine the mass hierarchy of neutrinos. If JUNO can interpret the mass of neutrinos before DUNE operates, the US project can then measure differently and confirm JUNO’s results.

They’re Khang (Theo Yahoo)