Overview
- Using data from August 26 to November 2, 2025, JUNO reported sin^2θ12 = 0.3092 ± 0.0087 and Δm^2_21 = (7.50 ± 0.12)×10^-5 eV^2, improving precision by a factor of 1.6 over previous results.
- The reactor-based measurement reproduces the previously noted ~1.5σ difference between solar and reactor determinations of θ12.
- A companion performance paper details 1,785 photoelectrons per MeV at the detector center, a 20.6 m attenuation length at 430 nm, and 3.4% energy resolution for two 0.511 MeV gamma rays.
- Operations achieved >99.9% muon-tagging efficiency in the water Cherenkov veto and a >97.8% data-acquisition duty cycle during initial runs.
- JUNO’s 20-kiloton liquid-scintillator detector—housed in a 35.4 m acrylic sphere and read out by over 45,000 PMTs—is run by more than 700 scientists from 74 institutions across 17 countries and now moves to determine the neutrino mass ordering.