AI 中文总结
利用DarkSide-50探测器在$^{36}$Ar中寻找双中微子双电子俘获，在约12吨·天暴露量下未发现显著过量，设定了半衰期限制，还评估了DarkSide-20k实验灵敏度，预计运行10年灵敏度将提高约100倍。
AI 中文摘要
双中微子双电子俘获是一种罕见的核衰变，即从原子壳层同时俘获两个电子并发射两个中微子。我们报告了首次利用DarkSide-50实验中来自地下源的低放射性液态氩靶，在$^{36}$Ar的$\textit{KK}$和$\textit{KL}$壳层中寻找双中微子双电子俘获。在约12吨·天的地下氩暴露量下未观察到统计学上显著的过量。考虑到地下氩中$^{36}$Ar的同位素丰度（0.007%），我们在90%置信水平下对$^{36}$Ar中双电子俘获过程的半衰期设定了$T_{1/2}>9.2×10^{19}$年的限制。还评估了未来几年将运行的DarkSide-20k实验的灵敏度，预计在10年预期运行且假设与DarkSide-50地下氩靶中$^{36}$Ar丰度相同时，灵敏度将提高约100倍。
英文摘要
Two-neutrino double electron capture is a rare nuclear decay where two electrons are simultaneously captured from the atomic shells and two neutrinos are emitted. We report on the first search for two-neutrino double electron capture in the $\textit{KK}$- and $\textit{KL}$-shells of $^{36}$Ar using the low-radioactivity liquid argon target from underground sources in the DarkSide-50 experiment. No statistically significant excess was observed with approximately 12 ton-day exposure of underground argon (UAr) and, taking into account the $^{36}$Ar isotopic abundance in UAr (0.007%), we set a limit on the half-life of the two-electron capture process in $^{36}$Ar of $T_{1/2} > 9.2 \times 10^{19}$ yr at 90% C.L. The sensitivity of the DarkSide-20k experiment, which will become operational in the next few years, was also evaluated and is expected to increase by a factor $\sim$100 with 10 years of expected operation and assuming the same $^{36}$Ar abundance as in the DarkSide-50 underground argon target.
Comments12 pages, 5 figures; corrected author list (added author A. Derbin, D. Semenov, E. Unzhakov, V. Muratova; updated author order)
