Direct dark matter search
The long-running project of our group is the direct experimental search for supersymmetric neutralino dark matter in an underground cell of the Kamioka Observatory. We employed various kinds of detectors aiming at a search for spin-dependently(SD) interacting neutralinos. In 2005, our results put a stringent limit to the SD cross section competitive to the then world records on it. The search has been suspended for the improvement of the detector in order to get higher background elimination ability which is essential to record the possible feeble neutralino signals.
Solar axion search
We are also running an experiment to search for axions, light neutral pseudoscalar particles yet to be discovered. The axion would be produced in the solar core through the Primakoff effect. It can be converted back to an x-ray in a strong magnetic field in the laboratory by the inverse process. We search for such x-rays coming from the direction of the sun with the TOKYO AXION HELIOSCOPE, aka Sumico. Sumico consists of a cryogen-free 4-Tesla superconducting magnet with an effective length of 2300 mm and PIN photodiodes as x-ray detectors. By now, we put the most stringent upper limits to the axion-photon-photon coupling constant for the axion mass region between 0.84 eV and 1.00 eV. This is a newly explored mass region which CERN Axion Solar Telescope(CAST) group that started later has not reached yet.
