After analyzing 59 days of valid data (from August 26th to November 2nd this year), the JUNO (Jiangmen Underground Neutrino Observatory) Collaboration measured the mixing angle θ₁₂ and the mass-squared differenceΔm²₂₁, which are the parameters that characterize solar neutrino oscillations. Their result improves upon the previous best experimental precision by a factor of 1.5 to 1.8.

Professor Wen Liangjian, Deputy Director of the Institute of High Energy Physics of the Chinese Academy of Sciences and Head of the physics analysis group of the JUNO Collaboration, explained that previously the two methods used to measure the mass-squared difference had shown a discrepancy of about 1.5 standard deviations, known as the "solar neutrino tension," which hinted at possible new physics. This time, the JUNO confirmed this tension through reactor neutrinos. In the future, the JUNO will be able to further confirm or refute this tension alone through simultaneous measurements of solar neutrinos and reactor neutrinos.

As a major international collaboration, JUNO brings together over 700 researchers from 75 institutions in 17 countries and regions. Marcos Dracos of the University of Strasbourg and the French National Centre for Scientific Research said that, as the chair of the JUNO Institutional Board, seeing this global effort reach such a milestone makes him very proud, and JUNO's success reflects the commitment and creativity of this entire international team.

With its ultra-high detection sensitivity, JUNO, in addition to focusing on its core goal of neutrino mass ordering, will also precisely measure neutrino oscillations, conduct studies of solar and supernova neutrinos, atmospheric neutrinos and geoneutrinos, and search for new physics beyond the Standard Model.

江门中微子实验首个物理成果探知了什么？

在经过了59天（今年8月26日至11月2日）有效数据分析后，江门中微子实验合作组测量了被称为“太阳中微子振荡参数”的混合角θ12和质量平方差Δm^2_21，得到的结果比此前实验的最好精度提高了1.5-1.8倍。

中国科学院高能物理研究所副所长、江门中微子实验合作组物理分析负责人温良剑介绍，此前这两种方法对质量平方差的测量结果有约1.5倍标准偏差的不一致，被称为“太阳中微子偏差”，暗示着可能有新物理。此次江门中微子实验通过反应堆中微子证实了这个偏差。未来，仅由江门中微子实验就能通过同时测量太阳中微子和反应堆中微子，进一步证实或证伪该偏差。

作为重大国际合作项目，江门中微子实验涵盖来自17个国家和地区、75个科研机构的700多名研究人员。“作为JUNO机构委员会主席，看到这一全球努力达到这样的里程碑，我感到非常自豪。”法国斯特拉斯堡大学、法国国家科学研究中心的Marcos Dracos说，“JUNO的成功反映了我们整个国际团队的投入和创造力。”

凭借其超高探测灵敏度，江门中微子实验除了聚焦中微子质量顺序这一核心目标，还将精确测量中微子振荡参数，开展对太阳、超新星、大气及地球中微子的研究，并寻找超出粒子物理标准模型的新物理。

文、图 | 记者 李钢
译丨郑奕玲
英文审校丨林佳岱