Director of Kamioka Observatory
Kamioka Observatory, Institute for Cosmic Ray Research, University of Tokyo, is located in Hida-city in the northern part of the Gifu prefecture. The entrance gateway is the Toyama airport in neighboring Toyama prefecture; it takes about 40 minutes to get from the airport to the Observatory. The permanent population of Higashi-Mozumi, Kamioka-town, where our research buildings and dormitory are located, is about 50. It is a quiet village in a lush natural setting. The Kamioka Observatory was established in 1995 to push forward with the Super-Kamiokande experiment (SK). This observatory is an inter-university facility and many scientists from various research institutions are conducting research here. The SK experiment is an international collaboration and about half of the 150 total collaborators come from foreign countries. Most of them belong to US institutions, but some are from Canada, Europe, Korea, and China.
Kamioka Observatory is a world frontier center of neutrino physics. Within two years of starting to take data in 1996, Super-Kamiokande had discovered neutrino oscillations through its observations of atmospheric neutrinos. This discovery revealed that neutrinos – previously considered to be massless – did indeed have finite masses, providing a vital clue to a new theoretical framework of elementally particle physics. K2K, the first long baseline neutrino oscillation experiment, confirmed the atmospheric neutrino oscillation discovery by using a beam of man-made neutrinos. As an extension of K2K, the T2K long baseline experiment using a new accelerator (JPARC) in Tokai started in April 2009. By June 2011 we had observed an indication of the last type of neutrino oscillation which had so far gone undetected.
Studies complementary to the flagship SK experiment are ongoing. Recently, our knowledge of matter and energy in the universe has increased greatly with the surprising realization that 23% of the universe is composed of some sort of dark matter that does not emit light but can still be observed by its gravitational effects. The main component of dark matter is expected to be a new type of elementary particle. Direct observation of dark matter will be a great help in understanding the structure of the universe. The construction of a liquid xenon detector (XMASS) to search for the dark matter has been completed and the detector has started its commissioning phase.
There’s more: a gravitational wave telescope has been developed, and a laser strain-meter and a superconducting gravimeter are observing vibrations and deformations of the earth for geophysical research. An experiment to search for dark matter using a different technology than that of XMASS is in progress. A double beta decay search experiment to study the nature of neutrinos and anti-neutrinos has been constructed. We call these new research fields in the underground laboratory “observational particle physics”.