Search for neutrino-less double beta decay of Ca-48 by CaF2 scintillator

摘要

A CaF2 scintillation detector system (ELEGANT VI) has been operating at Oto Cosmo Observatory to study double beta decays of Ca-48. No events were observed around the Q-value energy region after the analysis of 4.23 kg yr data. To derive the lower limit for the half-life of the neutrino-less double beta decay of Ca-48, the expected number of background events in that energy region was estimated by a Monte Carlo simulation using the measured activities of Bi-214 and Rn-220 inside CaF2 crystals. A new lower limit is obtained to be 1.4 x 10(22) yr at the 90% C.L. An experimental sensitivity is 5.9 x 10(21) yr at the 90% C.L. (C) 2003 Elsevier B.V. All rights reserved. [References: 22]