China’s Massive Neutrino Observatory Reveals First Major Discovery
- Ritambhara K
- 4 days ago
- 3 min read
Credit: Xinhua/Jin Liwang
The world’s largest transparent spherical neutrino detector, located in Guangdong Province in south China, has achieved its first major scientific milestone, marking a significant step forward in a project that has been under development for more than a decade.
The breakthrough was announced on Wednesday during a press conference held in Jiangmen by the Institute of High Energy Physics (IHEP) under the Chinese Academy of Sciences (CAS). At the event, IHEP deputy director Wen Liangjian presented the very first physics results from the Jiangmen Underground Neutrino Observatory, better known as JUNO.
According to Wen, JUNO has delivered remarkable results using just 59 days of effective data collected since its official start of operations on August 26 this year. Within this short period, the observatory successfully measured two critical solar neutrino oscillation parameters with a precision that is 1.5 to 1.8 times higher than anything achieved by previous experiments worldwide. These two parameters, originally determined through observations of solar neutrinos, can also be measured using reactor antineutrinos.
However, earlier attempts to compare outcomes from the two methods revealed a small but persistent 1.5-sigma discrepancy, informally known as the solar neutrino tension. This inconsistency has intrigued physicists for years, suggesting the possibility of previously unknown physics beyond the Standard Model.
Wang Yifang, JUNO’s project manager and spokesperson, emphasized how extraordinary it is for an experiment of this scale to reach such precision so early in its operation. “Achieving this level of accuracy within only two months shows that JUNO is performing exactly as it was designed to,” Wang said.
“With this performance, JUNO is poised to determine the ordering of neutrino masses, rigorously test the three-flavor neutrino oscillation framework, and potentially uncover new physics that goes beyond our current theoretical understanding.”
Neutrinos themselves are among the universe’s most mysterious and least understood particles. They rarely interact with matter, passing effortlessly through the human body, buildings, oceans, and even the entire Earth without leaving any trace—earning them the nickname “ghost particles.”
Because these particles are so elusive, studying them requires exceptionally large and sensitive detectors capable of capturing the faintest signals produced during the rare moments when a neutrino interacts with another particle.
At JUNO’s core lies one of the world’s most ambitious scientific instruments: a 20,000-tonne liquid scintillator detector housed inside a 35.4-meter-diameter acrylic sphere. This delicate sphere is supported by a massive 41.1-meter-diameter stainless-steel truss, all submerged within a 44-meter-deep pool of purified water.
Surrounding the sphere are more than 45,000 photomultiplier tubes (PMTs)—extremely sensitive light detectors designed to capture the tiny flashes of light created when a neutrino collides with a hydrogen nucleus in the liquid scintillator.
These flashes are then converted into electrical signals, allowing researchers to study the particle’s properties with exceptional precision. The system also includes magnetic shielding coils, specialized cables, and light baffles, forming a sophisticated and highly coordinated detection network.
JUNO is not only a technological achievement but also a shining example of global scientific collaboration. The project brings together more than 700 scientists from 75 institutions across 17 countries and regions. First proposed in 2008 and approved by CAS and Guangdong Province in 2013, the observatory began its underground construction in 2015 and finally started collecting scientific data in August 2025.
During the press conference, CAS Vice President Ding Chibiao highlighted JUNO’s importance as a major international collaborative project in fundamental research. He stated that the observatory reflects China’s ongoing commitment to scientific openness, cooperation, and shared progress.
Marcos Dracos from the University of Strasbourg—who serves as Chair of the JUNO Institutional Board—echoed this sentiment, emphasizing that JUNO’s success represents the collective dedication, expertise, and creativity of the global research community.
Designed to determine the neutrino mass ordering, measure oscillation parameters with sub-percent precision, and investigate a variety of neutrino sources—including solar, atmospheric, supernova, and geoneutrinos—JUNO stands at the forefront of particle physics research. Looking ahead, Cao Jun, director of IHEP and JUNO’s deputy spokesperson, expressed confidence that the observatory will continue producing groundbreaking discoveries and nurturing new generations of physicists for many decades to come.
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