Search for Exotic Nuclear Ultra-Rare Process and Ultra-Lowbackground Nuclear Spectroscopy
| Project/Area Number |
02452024
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| Research Category |
Grant-in-Aid for General Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Research Field |
核・宇宙線・素粒子
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| Research Institution | Osaka University |
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Principal Investigator |
OHSUMI Hideaki Dept. of Phys., Osaka Univ, (Research Associate), 理学部, 助手 (70176882)
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| Co-Investigator(Kenkyū-buntansha) |
TANAKA Jyunichi Dept. of Phys., Osaka Univ, (Research Associate), 理学部, 助手 (70236595)
SANO Hirokazu Dept. of Phys., Osaka Univ, (Research Associate), 理学部, 助手 (00205999)
KISHIMOTO Tadafumi Dept. of Phys., Osaka Univ, (Associate Professor), 理学部, 助教授 (90134808)
EJIRI Hiroyasu Dept. of Phys., Osaka Univ, (Professor), 理学部, 教授 (80013374)
柴田 徳思 東京大学, 原子核研究所, 教授 (80028224)
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| Project Period (FY) |
1990 – 1991
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| Project Status |
Completed (Fiscal Year 1991)
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| Budget Amount *help |
¥8,000,000 (Direct Cost: ¥8,000,000)
Fiscal Year 1991: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1990: ¥7,400,000 (Direct Cost: ¥7,400,000)
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| Keywords | Ultra-Lowbackground / Ultra rare process nuclear spectroscopy / Super Heavy Charged Particle / Charge non-conserving Decay / Dark Matter / 極低バックグランド / グ-クマタ- / WIMP |
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| Research Abstract |
The nuclear exotic ultra-rare decays and the possibility of the existence of exotic particles have been investigated by means of ultra rare process nuclear spectroscopy with ultra low background detectors. Abstracts studied are as follows :
1. Super heavy charged particle X- have been searched by using ^<100>Mo nucleus. We studied the exotic nuclear beta decay ^<100>MoX^- -> ^<100>TcX^- -> ^<100>RuX^-. The exotic decay was studied by using ultra low background Ge detector. The upper limit of the creation of such exotic nucleus ^<100>MoX^- is found to be 2.84.10^<-26> 1/sec/nucleus.
2. The charge non-conserving processes (CNC) were studied by exotic CNC beta decay of ^<100>Mo ->^<100>Tc+nu+ nu (a) and the CNC nuclear excitation of ^<127>I+e_K -> ^<127>I^*+nu (b). The possibility of the process (a) was investigated by measuring gamma-ray of the doughter of ^<100>Tc. The lower limit of the CNC beta decay is 1.1・10^<18>yr, which means the upper limit of the CNC coupling constant *^2_*(G_<cnc
… More
>/G_F)^2<2.3・10^<-20>. The CNC process (b) was studied by searching for the gamma decay from the first excited state of ^<127>I. Lower lirffit of the mean life was obtained 5.8・10^<23>yr, which means the upper limit of the coupling constant *^2_* (G_<cnc>/G_F)^2 < 1.1・10^<-24>.
3. Dark matter (DM), if there is in our galaxy, may interact to a nucleus in the detector via elastic collision. An ultralow background large volume NaI detector was used to search DAI candidates. As both ^<23>Na and ^<127>I nucleus in the NaI detector has a nonzero spin, NaI detector is very suitable to search for the DM candidates with only axdal vector couplings. In addition, the cross section of DM candidates with spin independent couplings is roughly proportional to the the square of the neutron number, ^<127>I nucleus is very effective to the detection of DM candidates with spin independent couplings. The pulse height effect of the recoil nucleon due to the DM scattering in the NaI detector have been directly measured by using neutron scattering. Our data shows the most stringent upper limit on the maximum halo density of the both candidate of Dirac neutrino and Majorana neutrino with mass heavier than about 10OGeV. Less
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Report
(3 results)
Research Products
(10 results)
