[Previous] | [Session 28] | [Next]

[28.01] Super-Kamiokande

Y. Totsuka (Tokyo), Super-Kamiokande Collaboration

Super-Kamiokande is a 50,000\,ton water-Cherenkov detector in which central 22,500\,ton water is used for a useful target material. It is located 1000\,m underground at Kamioka Observatory, Institute for Cosmic Ray Research, the University of Tokyo.

Low-energy (5\,MeV e< 50\,MeV) electron neutrinos (\nu_e) are detected with a reaction \nu_e+e arrow \nu_e + e where scattered electrons give signals. At high energies (100\,MeV < E_\ell \leq 100\,GeV), \nu_e and muon neutrinos (\nu_\mu) are detected with charged-current reactions \nu_e (\nu_\mu) + N arrow e (\mu) +X, where N is a nucleon and produced e or \mu give signals.

Super-Kamiokande is able to detect neutrino events from several neutrino sources; the Sun, supernovae, the atmosphere. It has been operational since April 1996.

We have successfully observed more than 10,000 solar-neutrino events. The observation confirmed the solar neutrino problem, i.e., a strong deficit of solar neutrinos compared with the standard-solar-model calculation. The most likely solution of the solar neutrino problem is neutrino oscillations, which take place if two neutrino species (\nu_e and one of the other species) mix and they have non-zero masses. We are currently working to find unambiguous evidence for the neutrino oscillations. The present status of this effort will be presented.

We have been watching neutrino bursts from supernovae which go off as far as a few 100\,kpc. If a supernova goes off at the center of our Galaxy, we expect more than 5,000 neutrio events. Expected signals and an early warning system of supernovae will be presented.