The successful completion of the Jiangmen Underground Neutrino Observatory (JUNO) and the release of its first physics results were announced by the Institute of High Energy Physics (IHEP) of the Chinese Academy of Sciences (CAS) at a press conference held in Jiangmen City on Nov. 19. 

After more than a decade of design, construction, and international collaboration, JUNO has become the world's first next-generation, large-scale, high-precision neutrino detector to begin operation. The detector's key performance indicators fully meet or surpass design expectations, confirming that JUNO is ready to deliver frontier measurements in neutrino physics. An article describing the detector performance has been submitted to Chinese Physics C and was posted on arXiv on Nov. 18.

The JUNO experiment’s first physics results were presented by Prof. WEN Liangjian, physics analysis coordinator of the JUNO Collaboration, at the press conference. An article reporting these findings has been submitted for publication, and was posted on arXiv on Nov. 18.

Using data collected between Aug. 26 and Nov. 2, 2025—59 days of effective data after the start of operation—JUNO has already measured the so-called solar neutrino oscillation parameters, θ₁₂ and Δm²₂₁, with a factor of 1.5 to 1.8 better precision than previous experiments. 

These parameters, originally determined using solar neutrinos, can also be precisely measured by reactor antineutrinos. Earlier results from the two approaches showed a mild 1.5-sigma discrepancy, sometimes called the solar neutrino tension, hinting at possible new physics. The new JUNO measurement confirmed this difference, which in future can be proved or disproved by the JUNO experiment only using both solar and reactor neutrinos.

"Achieving such precision within only two months of operation shows that JUNO is performing exactly as designed," said WANG Yifang, JUNO project manager and spokesperson. "With this level of accuracy, JUNO will soon determine the neutrino mass ordering, test the three-flavor oscillation framework, and search for new physics beyond it."

With its unprecedented detection sensitivity, JUNO will determine the neutrino mass ordering and measure oscillation parameters with sub-percent precision. It will also study solar, atmospheric, supernova, and geoneutrinos, and search for physics beyond the Standard Model. 

Designed for a scientific lifetime of about 30 years, JUNO can be upgraded into one of the world’s most sensitive detectors for neutrinoless double-beta decay, probing the absolute neutrino-mass scale and testing whether neutrinos are Majorana particles. "JUNO will continue to produce important results and train new generations of physicists for decades to come," said CAO Jun, director of IHEP and JUNO deputy spokesperson.

JUNO is a major international collaboration led by IHEP. The project involves more than 700 scientists from 75 institutions across 17 countries and regions. "As Chair of the JUNO Institutional Board, I am proud to see this global effort reach such a milestone. JUNO’s success reflects the commitment and creativity of our entire international community," said Marcos Dracos of the University of Strasbourg and CNRS/IN2P3 in France.

"Many factors contributed to this success, among which the convergence of experience and expertise in liquid scintillator detectors and related analysis techniques—brought together by groups from around the world—was surely pivotal in achieving JUNO’s unprecedented level of performance," added Gioacchino Ranucci of University and INFN of Milano in Italy, deputy spokesperson of JUNO.

The JUNO detector seen from outside. (Image by JUNO Collaboration)