Recently it has been confirmed by oscillation experiments that three types of neutrino have different masses. However, the absolute mass value has yet to be measured. Observation of neutrino-less double beta decay tells us the mass and verifies that the neutrino has a Majorana mass which violates the conservation of lepton number. It thus tells us why our universe has only matter (no antimatter). These studies can only be achieved at the low background conditions for which underground laboratories are best suited. We have been working in a 5km long tunnel at Oto, Nara. We are constructing a new big detector (CANDLES III) at the Kamioka underground laboratory, Gifu.
We are studying nuclear systems with strangeness. A neutron star is a single giant nucleus with strangeness. In order to understand the nature of the neutron star, we are studying kaon nucleus interaction which is a key to see whether kaon condensation takes place. Structure of hypernuclei, which we are also studying, gives similar information. We are preparing an experiment to study nuclei with strangeness at J-PARC, Ibaraki.
CANDLES III detector to measure neutrino-less double beta decay.
Beam line and spectrometer for strangeness nuclear physics at J-PARC