Neutrino-less double-β decay of Ca48 studied by CaF2(Eu) scintillators

We searched for the neutrino-less double-beta decay(0 nu beta beta) of Ca-48 by using CaF2(Eu) scintillators. Analysis of their pulse shapes was effective to reduce backgrounds. No events are observed in the Q(beta beta) value region for the data of 3394 kg center dot day. It gives a lower limit (90% confidence level) of T-1/2(0 nu beta beta)>2.7x10(22) year for the half-life of 0 nu beta beta of Ca-48. Combined with our previous data for 1553 kg center dot day [I. Ogawa , Nucl. Phys. A730, 215 (2004)], we obtained a more stringent limit of T-1/2(0 nu beta beta)>5.8x10(22) year.