STUDY OF 48-Ca DOUBLE BETA DECAY

Abstract

Neutrino-less double beta decay (0νββ) is currently known to be only experiment to verify whether lepton number conservation is violated. The violation is the key to create matter dominated universe by the so-called Leptogenesys. We have been studying double beta decay of 48 Ca . First stage of the experiment was carried out by using the ELEGANT VI detector system. We gave the best lower limit of the half life of 0νββ of 48 Ca . We have been developing CANDLES detector system to sense much longer life-time region. We have developed techniques to reduce further backgrounds. One of the techniques has been used in the ELEGANTS VI system and improved further the half life limit. The CADLES detector system will be installed Kamioka underground laboratory next year. I describe these studies.