Trillions of neutrinos pass through our bodies every second. The sun produces them through nuclear fusion. The same goes for nuclear power plants. Some come from supernova explosions in space. Neutrinos are paired with antineutrinos, which scientists believe mirror the behavior of neutrinos.

As such, JUNO is designed to capture antineutrinos, specifically the antineutrinos emitted by two nuclear power plants located approximately 53 miles from the observatory.

The 13-story JUNO sphere will be filled with a special liquid called a scintillator and submerged in a cylinder of purified water, said project leader Wang Yifang, director of the China Institute of High Energy Physics.

When the antineutrinos pass through the liquid, they trigger a chemical process that produces a brief burst of light that can be picked up by sensors inside the sphere.

“This event will cause a flash that will last only about 5 nanoseconds, and we hope to capture it with thousands of photomultiplier tubes surrounding the sphere,” he says, as a worker behind him says, Mr. Wang, wearing a helmet, spoke while installing the doubler. “We hope to catch 60 events per day.”

Thanks to its approach, JUNO should be able to measure differences in antineutrino masses about 10 times more accurately than previous instruments.

First of three new neutrino observatories

JUNO is part of China’s ambitious efforts to become a global scientific powerhouse. In a speech this year, President Xi Jinping laid out plans to transform the country into a science and technology superpower by 2035.

JUNO is expected to be the first of three next-generation neutrino observatories to open over the next decade, making it a kind of spearhead in a new era of physics. In Japan, the Hyper-Kamiokande Observatory is scheduled to open in 2027. And a U.S.-backed program called the Deep Neutrino Experiment (DUNE) calls for particle accelerators to send beams of neutrinos underground from Illinois to North Dakota starting in 2027. 2031.

The three upcoming observatories are both complementary and competitors, as they all plan to use different techniques to detect particles. Each project involves extensive international collaboration aimed at advancing the field, creating new spin-off technologies and training a new wave of scientists.

“When you start these experiments, it’s not unlikely that you’ll observe something unexpected,” said Chris Marshall, an assistant professor of physics at the University of Rochester who works on the DUNE project. “Trying to unravel these very complex effects will require multiple experiments measuring things in different ways.”

The ability of each observatory to answer important physics questions depends in part on how well researchers can collaborate between and among projects. But there is growing concern among some scientists around the world that rising geopolitical tensions between the United States and China, and the resulting deterioration in their scientific relations, could hinder progress. are.

In recent years, the United States has pursued policies to prevent Chinese scientists from bringing American-based technology to the country and to prevent China from poaching its scientific stars.

Wang said the U.S. is denying visa applications for 2022 and 2023 without explanation and limiting U.S. involvement in JUNO.

“In science, cooperation and competition are good, but it can’t be all about competition,” he said.

U.S.-based scientists also said they have found new obstacles to cooperation with Chinese scientists.

“From the U.S. side, it’s becoming increasingly difficult to obtain funding for collaborations with Chinese colleagues,” Patrick Huber, director of the Center for Neutrino Physics at Virginia Tech, said in an email. It has also become much more difficult for our Chinese colleagues to obtain U.S. visas.” .

“It’s not impossible to collaborate with Chinese scientists, but it’s becoming increasingly difficult,” said Ignacio Taboada, a physics professor at the Georgia Institute of Technology who directs an existing neutrino observatory in Antarctica. “I’m working on it,” he said.

Solving the mystery of neutrinos

The data generated by JUNO could go a long way toward solving important mysteries about how and why neutrinos change shape more than other elementary particles.

Neutrinos can oscillate, or transform, between three so-called “flavors” during their travels: muon, tau, and electron. For example, the sun sends electron neutrinos toward Earth, but they can also arrive as muon neutrinos. When neutrinos interact (which rarely happens), they settle on a particular flavor.

Additionally, scientists believe that neutrinos travel as one of three different mass states, and that state helps determine the likelihood of a neutrino interacting as a particular flavor. However, it is not yet clear which state has the largest population.

Scientists also found that neutrinos and antineutrinos may deform differently as they travel, and that those differences may account for some of the imbalance in the physics between matter and antimatter in the universe. I think there is.

If so, learning more about the masses and oscillations of neutrinos and antineutrinos will help researchers find a missing page in the Standard Model of physics (the rulebook of particles and their interactions), or something that has never been known before. This could help researchers understand whether missing particles or forces are having invisible effects. role.

“Our beautiful theory of reality, the Standard Model, is not the final theory,” said Sergio Bertolucci, an Italian particle physicist and DUNE co-spokesperson. “It turns out that we need to know more about neutrinos to answer things that the standard model can’t answer.”

Wang hopes JUNO will win the race to determine the neutrino mass hierarchy before the United States and other countries.

“We just want to be good scientists. In science, being first is most important. There’s nothing to be second,” he said. “As a scientist, I can’t always be a follower. I want to have my own thing.”

If JUNO explains the neutrino mass story before DUNE comes online, the U.S.-led project will be able to measure that question differently and confirm JUNO’s results.

DUNE’s plan is to measure neutrinos as they leave the Illinois facility, then travel 800 miles around Earth, where they can interact and oscillate. If the neutrinos arrive in South Dakota and can be detected, scientists could compare the flavor combinations of the neutrinos at the beginning and end of their journey. However, the project experienced delays and cost overruns.

“JUNO’s uniquely rich dataset, alone or in combination with other experiments, will play a key role in determining bulk orders by 2030,” said Professor Pedro Ochoa said in physics and astronomy from the University of California, Irvine.

However, several scientists involved in neutrino observation projects acknowledged that it is impossible to predict how much benefit the research will actually bring to Earth. They suggested that in the future, new technologies could be spun off, driving innovation in data-intensive computing and advancing particle accelerator science.

“We can’t make electric light by improving candles, so we need to take a step forward. We need a break,” said John C., a particle physicist at the U.S. Department of Energy’s Brookhaven National Laboratory and co-spokesperson for the DUNE project. Mary Bishai says. “Basic research inherently creates discontinuities.”

Wang put it another way, saying his work is driven by pure curiosity: “I work in ‘useless’ science.”