Status of 48Ca double beta decay search and its future prospect in CANDLES

CANDLES(CAlcium fluoride for the study of Neutrinos and Dark matters by Low Energy Spectrometer) is the experiment to search for the neutrino-less double beta decay(O nu beta beta) of Ca-48 with CaF2 scintillator. Ca-48 has the highest Q(beta beta)-value (4.3 MeV) among all isotope candidates for O nu beta beta. It enables us to measure signals with very low background condition. After rejection analysis with 131 days x 86 kg data for background events from radioactive contaminations in the CaF2 scintillators, no events are observed in the Q(beta beta)-value region. As a result, the Ovflfl half-life of Ca-48 is greater than 6.2 x 10(22) yr (90% confidence level). For further high sensitive measurement of Ca-48 O nu beta beta search, we have been developing the Ca-48 enrichment and CaF2 scintillating bolometer techniques. In this paper, the latest result for CANDLES and the status of scintillating bolometer development are described.