Scientists working to unlock the secrets of neutrinos have announced breakthrough results from a cutting-edge underground research facility in China, achieving the most accurate measurements ever recorded of specific characteristics of these mysterious subatomic particles.
The findings originate from JUNO, which stands for Jiangmen Underground Neutrino Observatory, a sophisticated particle detection system constructed approximately 2,130 feet beneath the surface under a hill close to Kaiping in China’s southern Guangdong province.
Researchers published their discoveries Wednesday in the journal Nature, drawing from information gathered during the detector’s inaugural operational phase following its completion last year – specifically during its first approximately 59 days of operation, spanning from August 26 through November 2.
“This is important not only because the numbers themselves are useful for neutrino physics, but also because they demonstrate the performance of JUNO as a new large-scale detector,” said Yifang Wang, a physicist at the Institute of High Energy Physics of the Chinese Academy of Sciences in Beijing and spokesperson for the JUNO Collaboration.
“This paper shows that the experiment has started from a solid foundation,” Wang said.
Alongside DUNE – which stands for the Deep Underground Neutrino Experiment – in the United States and the Hyper-Kamiokande experiment in Japan, JUNO represents one of three major flagship initiatives anticipated to advance neutrino research over the next several decades.
“Neutrinos are basic particles and are extremely abundant in the universe, but they remain among the least understood,” Wang said.
These particles can penetrate any material, seldom interacting with matter. Remarkably, countless trillions pass through human bodies each second without any detection on our part.
Created in locations such as the sun’s core and exploding stars known as supernovas, neutrinos exist in three varieties, or “flavors,” and can transform from one type to another through a process called oscillation during their journey. The mass difference, referred to as mass ordering, among neutrino varieties represents a crucial unsolved puzzle.
“JUNO’s central goal is to determine the neutrino mass ordering, meaning the ordering of the neutrino mass states. We know that neutrinos have mass, but we still do not know which mass state is the lightest and which is the heaviest,” Wang said.
“This first result is not yet a determination of the mass ordering. Its value is that it validates the detector and the analysis with real data,” Wang said.
JUNO successfully measured two of the six essential neutrino oscillation parameters with unprecedented accuracy, Wang explained, representing approximately 1.6 times greater precision than previous attempts.
Each particle type in ordinary matter possesses a corresponding antiparticle sharing identical mass but opposite electrical charge – whether positive, negative, or neutral, as applies to neutrinos. Consequently, every neutrino has a matching antineutrino.
JUNO’s primary methodology for measuring neutrino oscillations involves observing antineutrinos released from the Yangjiang and Taishan nuclear power facilities, located roughly 33 miles from the detection equipment. The two parameters concerned the characteristics of antineutrinos.
The JUNO detection system consists of a massive spherical container holding 20,000 tons of organic liquid that produces light in the dark setting when particles, including antineutrinos, travel through it.
Neutrinos qualify as elementary particles, indicating they contain no smaller components, positioning them among the universe’s basic building materials. Since neutrinos carry no electrical charge, even the most powerful magnetic fields cannot affect them. During their cosmic travels, neutrinos move freely through matter – including stars, planets, and all other objects.
Researchers can track these particles back to their origins, thereby gaining knowledge about some of the most powerful phenomena in the universe. They could hold the answer to comprehending matter’s origin and its dominance in the cosmos over antimatter, the characteristics of dark matter and dark energy, and the internal mechanics of supernovas.
Wang indicated that JUNO will examine neutrinos originating from the sun, Earth, the atmosphere, and potentially a future supernova.
“Enormous numbers of neutrinos pass through the Earth every second, but only a tiny fraction interact. That is why experiments like JUNO need very large detectors, deep underground sites, careful shielding and long-term stable operation,” Wang said.
JUNO, which required an investment exceeding $300 million, embodies an international scientific partnership. Wang noted that JUNO, DUNE, and Hyper-Kamiokande serve as complementary endeavors.
“They use different technologies and neutrino sources, so each brings a different perspective to some of the most important questions in neutrino physics. Together, they will provide a broader and more robust understanding of neutrino properties,” Wang said.
