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.

Early data show that the detector's key performance indicators fully meet or surpass design expectations, confirming that JUNO is ready to deliver frontier measurements in neutrino physics.

A detailed paper describing the detector performance has been submitted to Chinese Physics C and was posted on the arXiv preprint server. At a press conference, Prof. Wen Liangjian, physics analysis coordinator of the JUNO Collaboration, presented the experiment's first physics results.

Using data collected between August 26 and November 2, 2025—just 59 days of effective data after the start of operation—JUNO has already measured the so-called solar neutrino oscillation parameters, known as θ12 and Δm221, with a factor of 1.6 better precision than all previous experiments combined.

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 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 Yifang Wang, 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."

JUNO is a major international collaboration led by the Institute of High Energy Physics (IHEP) of the Chinese Academy of Sciences. The project involves more than 700 scientists from 74 institutions across 17 countries and regions.