The Jiangmen Underground Neutrino Observatory (JUNO) marked a major milestone in August 2025 as it began recording physics data. Within just two months, the experiment delivered results that outperformed findings from international projects running for more than twenty years, highlighting the extraordinary capabilities of the detector.

‍

Data gathered between 26 August and 2 November 2025 presents JUNO’s first scientific results, delivering the most accurate values to date of several key neutrino oscillation parameters. The findings open new implications for research into the origin of neutrino mass. [1], [2].

‍

Determination of the value and the comprehension of the origin of neutrino masses and flavour mixing is connected to major open questions in cosmology and astrophysics, including the matter–antimatter asymmetry of the universe, the nature of dark matter, and the evolution of astrophysical objects. Such precise measurements of neutrino oscillation parameters open also the door to more accurate tests of the completeness of the three-neutrino model.

‍

"JUNO is becoming a fundamental experiment for neutrino physics and neutrino cosmology in the coming decades."                                                                                 Vít Vorobel

‍

“JUNO is becoming a fundamental experiment for neutrino physics and neutrino cosmology in the coming decades. By combining cosmological observations and beta decay research, JUNO's precise results will provide an unprecedented narrowing of the range of many models of neutrino mass origin and neutrino mixing, and for new physics beyond the Standard Model,” explains Vít Vorobel, who is scientific team leader of the Faculty of Mathematics and Physics at Charles University.

‍

Neutrino oscillations indirectly indicate that neutrinos have non-zero masses, which is widely accepted as experimental evidence of physics "beyond the Standard Model." Neutrino oscillations are described by six parameters: two mass square differences ∆m²₂₁, ∆m²₃₂, three mixing angles θ₁₂, θ₁₃, θ₂₃, and one phase δ_CP, which violates CP invariance. Currently, the value of δ_CP and the sign of ∆m₃₂², which determines whether the neutrino state ν₃ is heavier or lighter than the states ν₁ and ν₂, remain unknown – the so-called "neutrino mass ordering question."

‍

Data collected by the JUNO experiment in the short time span between August 26 and November 2, 2025, provide the world's most accurate determination of two neutrino oscillation parameters. The accuracy of the mixing parameter sin² ⁡θ₁₂ was improved by a factor of 1.8 from 5.1% to 2.8% compared to previous measurements, and the precision of the mass square difference ∆m₂₁² was improved by a factor of 1.5 from 2.5% to 1.6%.

‍

JUNO is designed for 30 years of scientific operation with the possibility of upgrading to a world-leading experiment investigating double beta decay. Such an upgrade would determine the absolute values of neutrino mass and investigate whether neutrinos are Majorana particles. In doing so, it addresses fundamental questions linking particle physics, astrophysics, and cosmology that shape our understanding of the universe.

‍

‍

‍

‍

More about JUNO:

JUNO unites over 700 researchers from 74 institutions in 17 countries and regions, predominantly from China and Europe. Since the establishment oft he JUNO collaboration in 2013, a group of scientists and students from theFaculty of Mathematics and Physics of the Charles University has been an active member of the collaboration. The team leader is Vít Vorobel from the Institute of Particle and Nuclear Physics.

‍

JUNO is in southern China near city Jiangmen Guangdong Province. The device is located 700 metres underground, capable of detecting antineutrinos produced by the Taishan and Yangjiang nuclear power plants, located 53kilometres away, and measuring their energy spectrum with the highest accuracy.Contrary to alternative approaches, the determination of the order of neutrino masses in the JUNO experiment does not depend on the effect of passing of neutrinos through the Earth's mass.

‍

At the heart of the JUNO experiment there is a central liquid scintillator detector, located in the center of a cylindrical water pool. The stainless steel structure, with a diameter of 41.1 meters, supports an acrylic sphere filled with scintillator, with a diameter of 35.4 meters, 20,000 20" photomultipliers, 25,600 3" photomultipliers, electronics, cabling, magnetic field compensation coils, and optical panels. The photomultipliers operate independently, capturing light from scintillation interactions and converting it into electrical signals.

‍

What can we learn from particles reaching Earth with energies far exceeding anything achievable in man-made laboratories?  On March 13, high-school students from across the Czech Republic came to explore this question at the Pierre Auger International Masterclasses.

‍

Organized for the fourth time by the Institute of Physics of the Czech Academy of Sciences (FZU) and the Faculty of Nuclear Sciences and Physical Engineering at CTU (FNSPE), the event offered a full day of lectures and hands-on activities.

‍

The programme was opened by the Dean of FJFI, Václav Čuba, and the Director of FZU, and FORTE member, Michael Prouza, who encouraged students to follow their curiosity and consider a future career in science. The morning lectures introduced both the broader context and the experimental side of the field of astroparticle physics. FORTE researcher Margita Kubátová (FNSPE, FZU) gave a lecture about astroparticle physics and cosmic rays, explaining what happens when these particles enter the Earth’s atmosphere, what we know and do not know about them and why they are so interesting to study.

‍

‍

This was followed by FORTE WP2 leader Petr Trávníček (FZU), who introduced the Pierre Auger Observatory in Argentina, showcasing how scientists detect these extremely energetic cosmic rays and highlighting key discoveries from over 20 years of the observatory's operation. In the afternoon, the students transitioned from listeners to researchers.

‍

Using real data from the observatory’s surface detectors, they analyzed cosmic-ray events and reconstructed their energies and arrival directions. Their results demonstarted both the steepness of the energy spectrum and showed a minor trend towards an unisotropic nature of the arrival directions 8 EeV.

‍

This hands-on experience provided a unique glimpse into the daily work of an international scientific collaboration.The day concluded with a joint videoconference, connecting participants in Prague with students at other sites across Europe and with researchers at the Pierre Auger Observatory.

‍

Students discussed their results, gained insight into how a global scientific collaboration operates, and had the opportunity to ask questions, not only about science, but also about what a career in research looks like. Once again, the Pierre Auger Masterclasses proved to be an inspiring experience, combining real science, active learning, and lively discussion.

‍

‍

A public lecture titled The Mystery of Dark Energy: Why Is the Universe Still Accelerating? was held on 15 May at the Municipal Library in Prague. The talk was delivered by Professor Bharat Ratra of Kansas State University, recipient of the 2025 Julius Edgar Lilienfeld Prize of the American Physical Society. The event opened with remarks from Luke Meinzen, cultural attaché at the US Embassy, who together with Dr. Ignacy Wolak-Sawicki welcomed Professor Ratra to the venue.

‍

In his lecture, Professor Ratra outlined the modern standard model of cosmology, beginning with rapid inflation after the Big Bang and tracing the development of structure in the universe. The talk addressed unresolved questions, including the mismatch in current measurements of the expansion rate, and noted that future telescopes such as the James Webb Space Telescope may provide further data. The presentation also covered the scales of the universe and the limits of Earth‑based intuition, explaining the roles of dark matter and dark energy in shaping present‑day cosmological models.