Double Beta Decay and Neutrino

双贝塔衰变和中微子

基本信息

批准号：
61065005
负责人：
EJIRI Hiroyasu
金额：
$ 171.39万
依托单位：
Osaka University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Specially Promoted Research
财政年份：
1986
资助国家：
日本
起止时间：
1986 至 1990
项目状态：
已结题

项目摘要

1. Ultra-low background beta-ray and gamma-ray detectors ELEGANTS (ELEctron GAmma-ray NeuTrino Spectrometer) III, IV, V have been developed. By investigating double beta decays and other rare decay process, conservation laws, properties (mass, helicity) of neutrino and new particles have been studied.2. ELE-III gave a lower limits of half lives : t>0.7X10^<23>years (y) and t > 0.6X10^<23>y for the neutrinoless double beta decays (0nubetabeta) of ^<76>Ge 0^+ -> 0^+ and 0^+ -> 2^+. The former was almost same level of other results and set limit of m_<nu>< 4eV on neutrino mass and the latter gave most stringent limit on the right-handed current.3. ELE-IV gave a lower limit of t > 5.4 X 10^<18>y for two neutrino double beta decay (0nubetabeta) of ^<100>Mo. This was the most stringent limit at that time (1989).4. ELE-V gave a finite value of tー1.5X10^<19>y for the 2nubetabeta of ^<100>Mo. This is the first result in the world by the counter method alone. It gives the 0nubetabeta nuclear matrix element. It gave the most stringent lower limit of t > 0.6X10^<22>y (m_<nu> <6eV) for the 0nu betabeta.5.The sensitivity of the ELE-V is 10^<23>y for a half life of 0nubetabeta, corresponding to m_<nu> -1eV region.6. Lower limits of t > 10^<20> - 10^<22>y for the double strangeness exchange weak decays (*S=2) NN->H (unddss) exclude the light H particle with the mass below 2m_N (1875MeV).7. By using 0.77 ton of NaI detector in ELE-V, a lower limit of t > 0.6X10^<23>y was obtained for charge nonconserving nuclear excitation. It sets upper limits of 3X10^<-25> and 1.5X10^<-40> on branching ratio of charge nonconservation mediated by the weak boson and photon. A lower lmit of 3.2X10^<23>y (preliminary) on a half life of the Kーelectron annihilation or the violation of Pauli exclusion principle through L to K-shell transition was obtained. These results were most stringent test of the charge conservation.8. A new region of spinーcoupled dark matter were surveyed.

1. 超低本底β射线和伽马射线探测器ELEGANTS（电子伽玛射线中微子能谱仪）III、IV、V是通过研究双β衰变过程和其他稀有衰变过程、守恒定律、性质（质量）而开发出来的。中微子和新粒子的螺旋性）已被研究。2．ELE-III给出了半衰期的下限：t>0.7X10^23年（y）和^<76>Ge 0^+ -> 0^+ 和 0^+ -> 2^+ 的无中微子双贝塔衰变 (0nubetabeta) t > 0.6X10^<23>y 前者与其他几乎相同水平。结果对中微子质量设定了m_<nu><4eV的限制，后者对右手电流给出了最严格的限制。 3． ^<100>Mo 的两个中微子双β衰变(0nubetabeta)的t > 5.4 X 10^<18>y 这是当时最严格的限制(1989)。4。 ^<100>Mo 的 2nubetabeta 的 tー1.5X10^<19>y 这是世界上第一个用计数器方法得到的结果。它给出了 0nubetabeta 核矩阵元素。它给出了 0nu betabeta.5 的最严格下限 t > 0.6X10^<22>y (m_<nu> <6eV)。 10^<23>y 的半衰期为 0nubetabeta，对应于 m_<nu> -1eV 区域。6. 10^<20> - 10^<22>y 用于双陌生交换弱衰变 (*S=2) NN->H (unddss) 排除质量低于 2m_N (1875MeV) 的轻 H 粒子。 7. ELE-V中0.77吨NaI探测器，对于电荷非守恒核获得t>0.6X10^23y的下限它设定弱玻色子和光子介导的电荷非守恒分支比的上限为3X10^<-25>和1.5X10^<-40>，下限为3.2X10^<23>y（初步）。获得了 K 电子湮灭或通过 L 到 K 壳层跃迁违反泡利不相容原理的半衰期。这些结果是对电荷最严格的测试。 8. 调查了一个新的自旋耦合暗物质区域。