The absolute mass scale of neutrinos is an intriguing open question in contemporary physics. The as-yet-unknown mass of the lightest and, at the same time, most abundant massive elementary particle species bears fundamental relevance to theoretical particle physics, astrophysics, and cosmology. The most model-independent experimental approach consists of precision measurements of the kinematics of weak decays, notably tritium β decay. With the KATRIN experiment, this direct neutrino-mass measurement has entered the sub-eV domain, recently pushing the upper limit on the electron-based neutrino mass down to 0.8 eV (90% CL) on the basis of first-year data out of ongoing, multiyear operations. Here, we review the experimental apparatus of KATRIN, the progress of data taking, and initial results. While KATRIN is heading toward the target sensitivity of 0.2 eV, other scientific goals are pursued. We discuss the search for light sterile neutrinos and an outlook on future keV-scale sterile-neutrino searches as well as further physics opportunities beyond the Standard Model.

中文翻译：

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用 KATRIN 实验探测中微子质量尺度


中微子的绝对质量尺度是当代物理学中一个有趣的悬而未决的问题。最轻但同时也是最丰富的质量基本粒子种类的质量尚不清楚，与理论粒子物理学、天体物理学和宇宙学具有根本相关性。最独立于模型的实验方法包括对弱衰变的运动学进行精确测量，特别是氚β衰变。通过 KATRIN 实验，这种直接中微子质量测量已进入亚 eV 领域，最近根据正在进行的多年运行的第一年数据，将基于电子的中微子质量的上限降低到 0.8 eV （90% CL）。在这里，我们回顾了 KATRIN 的实验装置、数据采集的进展和初步结果。虽然 KATRIN 正朝着 0.2 eV 的目标灵敏度迈进，但正在追求其他科学目标。我们讨论了轻无菌中微子的搜索和对未来 keV 尺度无菌-中微子搜索的展望，以及标准模型之外的更多物理机会。