论文标题
双β衰减的第一限制$^{\ bf 232} $ th
First limits on double beta decays in $^{\bf 232}$Th
论文作者
论文摘要
作为原始放射性同位素之一，$^{232} $ th主要经历$α$ -DECAY，半衰期为$ 1.402 \ times 10^{10} $ yr。但是，它也是35个双重β衰变候选者之一，其中禁止或严重抑制了单个$β$ -DECAY。在Gran Sasso Underground Laboratory（LNGS）的HPGE井检测器中测量了气体套中包含的181毫克thor，总暴露于3.25 g $ \ $ \ times $ d。我们在$^{232} $ th的所有双β衰减模式上获得了半衰期的限制，以$^{232} $ u的激发状态$ 10^{11-15} $ yr。对于最有可能过渡到$ 0_1^+$状态，我们发现较低的半衰期限制为$ 6.3 \ times 10^{14} $ yr（90％可信度）。这些是在$^{232} $ th中的双β衰减激发状态过渡的第一个约束。
As one of the primordial radioactive isotopes, $^{232}$Th mainly undergoes $α$-decay with a half-life of $1.402 \times 10^{10}$ yr. However, it is also one of 35 double beta decay candidates in which the single $β$-decay is forbidden or strongly suppressed. 181 mg of thorium contained in a gas mantle was measured in an HPGe well-detector at the Gran Sasso Underground Laboratory (LNGS) with a total exposure of 3.25 g $\times$ d. We obtain half-life limits on all double beta decay modes of $^{232}$Th to excited states of $^{232}$U on the order of $10^{11-15}$ yr. For the most likely transition into the $0_1^+$ state we find a lower half-life limit of $6.3 \times 10^{14}$ yr (90% credibility). These are the first constraints on double beta decay excited state transition in $^{232}$Th.
