Study of 48Ca double beta decay by CANDLES

CANDLES is the project to search for double beta decay (DBD) of 48Ca by using CaF2 scintillators. The Q-value of 48Ca, which is the highest (4.27 MeV) among potential DBD nuclei, is far above energies of γ-rays from natural radioactivities (maximum 2.615 MeV from 208Tl decay), therefore we can naturally expect small backgrounds in the energy region we are interested in. We have constructed the prototype detector, CANDLES III in our laboratory (Osaka U.) at sea level and studied the basic performance of the system, including the light collection, position reconstruction and background rejection. After R&D study we moved the detector system to new experimental room at Kamioka underground laboratory. Herein the expected performances and current status of the CANDLES system are described.