China's Giant Underground Neutrino Observatory Releases Its First Results

China's new JUNO neutrino observatory has delivered world-leading measurements after just 59 days, offering the most precise readings yet of two key neutrino oscillation parameters. "The physics result is already world-leading in the areas that it touches," says particle physicist Juan Pedro Ochoa-Ricoux of the University of California, Irvine, who co-leads a team on JUNO. "In particular, we measured two neutrino oscillation parameters, and that measurement is already for both parameters the best in the world." The results were published in two separate preprints on arXiv.org. Scientific American reports: JUNO's spherical detector, which is akin to a 13-story-tall fishbowl, primarily measures so-called electron antineutrinos spewing from the nearby Yangjian and Taishan nuclear plants. When the particles strike a proton inside the detector, a reaction triggers two light flashes that ping photomultiplier tubes and get converted into electrical signals. The new measurements from these neutrino-proton collisions are now considered the most precise for two oscillation parameters, which act as proxies for differences in their mass, according to Ochoa-Ricoux. "It is the first time we've turned on a scientific instrument like JUNO that we've been working on for over a decade. It's just tremendously exciting," Ochoa-Ricoux says. "And then to see that we're able to already do world-leading measurements with it, even with such a small amount of data, that's also really exciting." Still, the physicists will need years' worth of neutrino detections to answer the mass-ordering conundrum.

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