标题： 在 MAJORANA DEMONSTRATOR 的 26 kg-yr 探测暴露下对$^{76}$Ge 中无中微子双β衰变的搜索 显示英文标题

标题： A Search for Neutrinoless Double-Beta Decay in $^{76}$Ge with 26 kg-yr of Exposure from the MAJORANA DEMONSTRATOR

摘要： Majorana合作组正在使用高纯度Ge探测器阵列，以寻找$^{76}$Ge的无中微子双β衰变。 Majorana演示器由44.1千克的Ge探测器（其中29.7千克富集到88%的$^{76}$Ge）组成，分为两个模块，这两个模块由超净材料构建。 两个模块都包含在一个低本底屏蔽体内，位于南达科他州利德的桑福德地下研究设施中。 我们展示了关于在$^{76}$Ge中寻找无中微子双β衰变的更新结果，其富集暴露量为$26.0\pm0.5$千克-年。 凭借探测器在$Q_{\beta\beta}$处前所未有的能量分辨率 2.53 keV FWHM，我们在感兴趣区域内观察到一个事件，而估计的背景预期为 0.65 个事件，从而得到了$^{76}$Ge 无中微子双β衰变半衰期的下限为$2.7\times10^{25}$年（90% CL），其中位灵敏度为$4.8\times10^{25}$年（90% CL）。 根据所使用的矩阵元，获得了 200-433 meV 范围内有效马约拉纳中微子质量的 90% CL 上限。 在低本底配置中测得的本底为$11.9\pm2.0$个/(FWHM t yr)。 显示英文摘要

摘要： The MAJORANA Collaboration is operating an array of high purity Ge detectors to search for the neutrinoless double-beta decay of $^{76}$Ge. The MAJORANA DEMONSTRATOR consists of 44.1 kg of Ge detectors (29.7 kg enriched to 88% in $^{76}$Ge) split between two modules constructed from ultra-clean materials. Both modules are contained in a low-background shield at the Sanford Underground Research Facility in Lead, South Dakota. We present updated results on the search for neutrinoless double-beta decay in $^{76}$Ge with $26.0\pm0.5$ kg-yr of enriched exposure. With the DEMONSTRATOR's unprecedented energy resolution of 2.53 keV FWHM at $Q_{\beta\beta}$, we observe one event in the region of interest with 0.65 events expected from the estimated background, resulting in a lower limit on the $^{76}$Ge neutrinoless double-beta decay half-life of $2.7\times10^{25}$ yr (90% CL) with a median sensitivity of $4.8\times10^{25}$ yr (90% CL). Depending on the matrix elements used, a 90% CL upper limit on the effective Majorana neutrino mass in the range of 200-433 meV is obtained. The measured background in the low-background configurations is $11.9\pm2.0$ counts/(FWHM t yr).