The ULB JUNO group is delighted to share an important milestone for JUNO, the world’s largest underground neutrino detector. After ten years of design and construction, the JUNO experiment started data taking on 26 August 2025, with the central detector fully filled with 20,000 tonnes of liquid scintillator. Initial trial operation and data taking show that key performance indicators met or exceeded design expectations, enabling JUNO to tackle one of this decade’s major open questions in particle physics: the ordering of neutrino masses. JUNO will also deliver order‑of‑magnitude improvements in the precision of several neutrino‑oscillation parameters and enable cutting‑edge studies of neutrinos from the Sun, supernovae, the atmosphere, and the Earth. It will also open new windows to explore unknown physics, including searches for sterile neutrinos and proton decay.
The ULB joined the JUNO experiment in 2015 and has actively contributed to the construction of the detector. The ULB JUNO group, based at the IIHE (Interuniversity Institute for High Energies ULB-VUB), took responsibility for developing the back-end cards (BECs) of the electronics readout system, covering design, testing, production, and installation. This is a crucial element of the experiment, as it allows to trigger the most interesting events that will be stored and analyzed. The ULB JUNO team is actively involved in physics analysis preparation, detector commissioning, and calibration, and is analyzing the very first data. The team plays a key role in optimizing the detection of atmospheric neutrinos in JUNO. The group is additionally engaged in the detection of neutrinos from potential core-collapse supernova events and contributes to an international alert network. Finally the ULB team participates in detector calibration, using reference signals from natural radioactivity as well as external sources placed inside the detector.
Link to the JUNO Collaboration press release :
JUNO_PressRelease_26Aug2025.pdf
link to the ULB JUNO group press release :
ULB_PressRelease_JUNO_started_Data_Taking_26Aug2025.pdf