KamLAND-PICO Dark Mater Search Project

Dark matter search project KamLAND-PICO is proposed. The first phase of the project aims to verifying the annual modulation signal which has been reported by DAMA/LIBRA. The last phase of the project aims to determining the type of interaction between WIMPs and nucleus. The thin and wide area NaI(Tl) detector PICO-LON has been developed to determine the type of WIMPs interaction. The good performance of PICO-LON detector was obtained. The energy threshold was as low as 2 keVee and the the energy resolution was as small as 25% at 60 keVee. The highly pure NaI(Tl) crystal has been developed in collaboration with the Japanese developer. The purity of U and Th chain contaminants have been reduced to the order of a few tens of ppt. It should be remarked that the concentration of 210Pb was reduced to about 60 μBq/kg. The sensitivity to spin-independent WIMPs are discussed by applying 170 modules of NaI(Tl) with the dimension of 5 inch ϕ× 5 inch.