Physik Department, Technische Universität München, D-85748 Munich, Germany.
National Research Centre "Kurchatov Institute," Moscow 123182, Russia.
Science. 2019 Sep 27;365(6460):1445-1448. doi: 10.1126/science.aav8613. Epub 2019 Sep 5.
A discovery that neutrinos are Majorana fermions would have profound implications for particle physics and cosmology. The Majorana character of neutrinos would make possible the neutrinoless double-β (0νββ) decay, a matter-creating process without the balancing emission of antimatter. The GERDA Collaboration searches for the 0νββ decay of Ge by operating bare germanium detectors in an active liquid argon shield. With a total exposure of 82.4 kg⋅year, we observe no signal and derive a lower half-life limit of > 0.9 × 10 years (90% C.L.). Our sensitivity, assuming no signal, is 1.1 × 10 years. Combining the latter with those from other 0νββ decay searches yields a sensitivity to the effective Majorana neutrino mass of 0.07 to 0.16 electron volts.
中微子是马约拉纳费米子的发现将对粒子物理和宇宙学产生深远的影响。中微子的马约拉纳性质将使无中微子双β（0νββ）衰变成为可能，这是一种没有反物质平衡发射的物质创造过程。GERDA 合作组织通过在主动液态氩屏蔽中操作裸锗探测器来寻找 Ge 的 0νββ 衰变。在 82.4 kg·年的总曝光量下，我们没有观察到信号，并得出半衰期下限 > 0.9×10 年（90%置信区间）。假设没有信号，我们的灵敏度为 1.1×10 年。将后者与其他 0νββ 衰变搜索的灵敏度相结合，可得出有效马约拉纳中微子质量的灵敏度为 0.07 到 0.16 电子伏特。
