| Project/Area Number |
07404010
|
|---|
| Research Category |
Grant-in-Aid for Scientific Research (A)
|
| Allocation Type | Single-year Grants |
|---|
| Section | 一般 |
|---|
| Research Field |
素粒子・核・宇宙線
|
|---|
| Research Institution | The University of Tokyo |
|---|
Principal Investigator |
TOTSUKA Yoji The Univ.of Tokyo, ICRR,Professor, 宇宙線研究所, 教授 (40011712)
|
|---|
| Co-Investigator(Kenkyū-buntansha) |
FUKUDA Yoshiyuki The Univ.of Tokyo, ICRR,Research Associate, 宇宙線研究所, 助手 (40272520)
SHIOZAWA Masato The Univ.of Tokyo, ICRR,Research Associate, 宇宙線研究所, 助手 (70272523)
ITOW Yoshitaka The Univ.of Tokyo, ICRR,Research Associate, 宇宙線研究所, 助手 (50272521)
西川 公一郎 東京大学, 原子核研究所, 教授 (60198439)
大山 雄一 東京大学, 高エネルギー物理学研究所, 助手 (30213896)
井上 邦雄 東京大学, 宇宙線研究所, 助手 (10242166)
梶田 隆章 東京大学, 宇宙線研究所, 助教授 (40185773)
|
|---|
| Project Period (FY) |
1995 – 1997
|
| Project Status |
Completed (Fiscal Year 1997)
|
| Budget Amount *help |
¥33,600,000 (Direct Cost: ¥33,600,000)
Fiscal Year 1997: ¥2,300,000 (Direct Cost: ¥2,300,000)
Fiscal Year 1996: ¥24,700,000 (Direct Cost: ¥24,700,000)
Fiscal Year 1995: ¥6,600,000 (Direct Cost: ¥6,600,000)
|
|---|
| Keywords | proton decay / supersymmetry / grand unification / Super-Kamiokande / 陽子 / 水チェレンコフ光 / チェレンコフ |
|---|
| Research Abstract |
A proton decay mode p*nuK^+ has been searched for with a 50,000ton water Cherenkov detector "Super-Kamiokande". A search was carried out specifically by looking for a delayd coincidence signal of a gamma ray and a muon which are produced from an Oxygen decay
^<16>O* ^<15>N^<**>+K^++nu, ^<15>N^<**>* ^<15>N+gamma, K^+*mu^++nu.
We first made a light emitter which simulates Cherenkov light from the gamma ray and muon taking into account of their energies and angles. The light emitter was then lowered into the Super-Kamiokande detector and the detection efficiency of the gamma ray and muon was studied. It was found that the efficiency was excellent up to 5nsec of delay time, which is sufficient for the present search.
We then analyzed the 414 day-data obtained by Super-Kamiokande. The results are the following : We have not found evidence for the proton decay and therefore set the lower limit of proton lifetime divided by the branching ratio (tau/B) ;
From the muon energy-spectrum------2.8*10^<32> years,
From the Kaon decay pi^++pi^0-----1.3*10^<32> years,
From the present analysis gamma+mu---1.5*10^<32> years,
These results are the strongest limit on the proton decay p*nuK in the world. The present method will eventually provide the most sensitive limit, since the search is free from background.
|
