Abstrakt
The double-beta decay of Se-82 to the 0(1)(+) excited state of Kr-82 has been studied with the NEMO-3 detector using 0.93 kg of enriched Se-82 measured for 4.75 y, corresponding to an exposure of 4.42 kg.y. A dedicated analysis to reconstruct the gamma-rays has been performed to search for events in the 2e2 gamma channel.
No evidence of a 2 nu beta beta decay to the 0(1)(+) state has been observed and a limit of T-1/2(2 nu) (Se-82, 0(gs)(+) -> 0(1)(+)) > 1.3 x 10(21) y at 90% CL has been set. Concerning the 0 nu beta beta decay to the 0(1)(+)-state, a limit for this decay has been obtained with T-1/2(0 nu) (Se-82, 0(gs)(+) -> 0(1)(+)) > 2.3 x 10(22) y at 90% CL, independently from the 2 nu beta beta decay process.
These results are obtained for the first time with a tracko-calo detector, reconstructing every particle in the final state. (C) 2020 Elsevier B.V. All rights reserved.