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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.研制了超低本底β射线和γ射线探测器ELEGANTS（ELEctron伽马射线中微子谱仪）III、IV、V。通过研究双β衰变和其他罕见的衰变过程，研究了中微子和新粒子的守恒定律、性质（质量、螺旋度）. ELE-III给出了半衰期的下限：对于<23><23>^<76>Ge 0^+ -> 0^+和0^+ -> 2^+的无中微子双β衰变（0 nubetabeta），t> 0.7 × 10 ^年（y）和t > 0.6 × 10 ^年（y）。前者与其他结果基本相当，并将<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 ><18>^ Mo的两个中微子双β衰变（0 ~ nubetabeta）的极限设定为m_ 5.4 × 10^ y<100>。这是当时（1989年）最严格的限制。ELE-V给出了^ Mo的2倍数的有限值t = 1.5 × 10 ^<19>y<100>。这是世界上第一个单独使用计数器方法的结果。它提供了0核塔贝塔核基质元素。它给出了0 nu β的最严格下限t > 0.6 × 10 ^<22>y（m_<nu><6 eV）。5.对于0 nu β的半衰期，ELE-V的灵敏度为10^<23>y，对应于m_<nu>-1eV区域。双<20><22>奇异交换弱衰变（*S=2）NN->H（unddss）的t > 10^ - 10^ y的下限不包括质量低于2m_N（1875 MeV）的轻H粒子。在ELE-V中使用0.77吨NaI探测器，得到了非电荷守恒核激发的下限t > 0.6 × 10 ~（-1）<23>y。它对<-25><-40>弱玻色子和光子介导的电荷不守恒分支比设定了3 × 10 ^和1.5 × 10 ^的上限。得到了K电子湮没半衰期的下限为3.2 × 10 ~（-1）y<23>（初始值），即从L到K壳层跃迁违反Pauli不相容原理。这些结果是对电荷守恒性的最严格的检验.观测到一个新的自旋偶合暗物质区域。