1986 Fiscal Year Final Research Report Summary
An Experiment on Proton Decay.
Grant-in-Aid for General Scientific Research (A)
|Allocation Type||Single-year Grants |
|Research Institution||Institute for Cosmic Ray Research, University of Tokyo |
SUDA Teruhiro Institute for Cosmic Ray Research, University of Tokyo -> 東大, 宇宙線研究所, 助教授 (30011555)
高橋 嘉右 高エネルギー物理学研究所, 教授 (90004283)
SUZUKI Atsuto Department of Physics, University of Tokyo, 理学部, 助手 (00100818)
TOTSUKA Yoji Department of Physics, University of Tokyo, 理学部, 助教授 (40011712)
KOSHIBA Masatishi Department of Physics, University of Tokyo, 理学部, 教授 (00011461)
KIFUNE Tadashi Institute for Cosmic Ray Research, University of Tokyo, 宇宙線研究所, 助教授 (40011621)
TAKAHASHI Kasuke KEK,National Laboratory for High Energy Physics
|Project Period (FY)
1985 – 1986
|Keywords||Nucleon Decay / Proton Decay / Grand Unified Theory / Neutron Anti-neutron Oscillation / Monopole / Neutrino Oscillation / Astronomical Neutrino / Solar Neutrino / Cygnus X-3 / Supernova / Neutrino Burst / SN1987a|
The purpose of this project is to test experimentally for the Grand Unified Theories of the elemental particles by using a 3000 ton imaging water Cerenkov detector operated in the Kamioka mine. The subject to be performed are; searches for nucleon decays, n- <n!-> oscillation, magnetic monopoles, and neutrino oscillation. Observations of astronomical neutrinos, solar <^8B> neutrino. and neutrino burst from supernova explosion were also done with the same detector.
Nucleon Decays: For an exposure time of 1900 ton yr, the grate majority of fully contained events are naturally explained as due to cosmic ray neutrino interactions. No event of p <Forward Arrow> <e^+> <> pi <^。> , which is predicted by the standard SU(5) theory as a dominant decay mode of proton,was observed. This reduces the lower limit on partial lifetime for this mode to be 1.5x <10^(32)> yr at 90 % C.L. The lower limits on lifetimes for most of other decay modes are obtained to be between <10^(31)> yr and <10^(32)> yr. Th
ese results suggest strongly that the minimal SU(5) model must be modified.
n- <n!-> Oscillation: No n- <n!-> oscillation in a <^(16)O> nucleus was observed, and the lower limit on neutron lifetime in <^(16)O> is 4.3x <10^(31)> yr at 90 % C.L. corresponding to a lower limit of 1.2x <10^8> sec at 90 % C.L. for the neutron-antineutron oscillation time.
A search for Magnetic Monopoles: Search for low energy ( 30<E<52 MeV ) neutrinos from the Sun resulting from proton decays catarized by gravitationally trapped magnetic monopoles in the solar interia gives a limit of the monopole flux near the solar system to be <F_M> <1.6x <10^(-21)> ( <beta> / <10^(-3)> ) <^2> <cm^(-2)> <s^(-1)> <sr^(-1)> at 90 % C.L.
Neutrino Oscillation: From the analysis of observed zenith angle distrubution of atmospheric <> nu <_> mu <> and <> nu <_e> , the region of neutrino oscillation parameters of the mass difference <DELTA> <m^2> <Greater Than or Similar> <10^(-4)> <eV^2> , and the mixing angle <sin^2> 2 <theta> >0.5 is excluded.
Solar neutrino: The flux limit of solar <^8B> neutrino searched by <> nu <_e> e <Forward Arrow> <> nu <_ee> scattering is obtained to be < 3.3x <10^6> <> nu <_es> / <cm^2> sec. at 90 % C.L. This flux limit is less than that of predicted value by the standard solar model. This is the first result measured by a direct counting method.
Neutrino from Supernova: Neutrino burst from the Large Magellanic Cloud (LMC) SN1987a was observed on 23 February 7:35:35 UT during a time interval of 13 seconds. The signal consisted of ll electron events of 7.5 MeV to 36 MeV of which the first 2 point back to LMC. Number of events,energy distribution and time distribution is consistent with the gravitational collapse of the star with mass of 10 M <Of Sun> to 15 M <Of Sun> . This is the first historical observation of neutrino astronomy. Less
Research Products (11 results)