Neutrinoless double beta decay (DBD) is a useful probe to study neutrino properties such as the Majorana nature, the absolute neutrino mass, the CP phase and the others, which are beyond the standard model. The nuclear matrix element (NME) for DBD is crucial to extract the neutrino properties from the experimental transition rate. The neutrino-mass sensitivity, i.e., the minimum neutrino-mass to be measured by the DBD experiment, is very sensitive to the DBD NME. Actually, the NME is one of the key elements for designing the DBD experiment. Theoretical evaluation for the DBD NME, however, is very hard. Recently experimental studies of charge-exchange nuclear and leptonic reactions have shown to be used to get single-β$\beta$ NMEs associated with the DBD NME. Critical discussions are made on the neutrino-mass sensitivity and the NME for the DBD neutrino-mass study and on the experimental studies of the single-β$\beta$ NMEs and nuclear structures associated with DBD NMEs.

中文翻译：

---

中微子双β衰变的中微子质量敏感性和核基质元素

无中微子双β衰变（DBD）是研究中微子特性（例如Majorana性质，绝对中微子质量，CP相等）的有用探针，超出了标准模型。DBD的核基质元素（NME）对于从实验转变速率中提取中微子特性至关重要。中微子质量灵敏度，即通过DBD实验测量的最小中微子质量，对DBD NME非常敏感。实际上，NME是设计DBD实验的关键元素之一。但是，对DBD NME进行理论评估非常困难。最近进行的电荷交换核反应和轻子反应的实验研究已证明可用于获得单β$\beta$与DBD NME关联的NME。关于DBD中微子质量研究的中微子质量敏感性和NME以及单β的实验研究进行了重要的讨论$\beta$ NME和与DBD NME相关的核结构。