Search for the double-beta decay of 82Se to the excited states of 82Kr with NEMO-3

Abstract The double-beta decay of 82Se to the 0 1 + excited state of 82Kr has been studied with the NEMO-3 detector using 0.93 kg of enriched 82Se measured for 4.75 y, corresponding to an exposure of 4.42 kg⋅y. A dedicated analysis to reconstruct the γ-rays has been performed to search for events in the 2e2γ channel. No evidence of a 2 ν β β decay to the 0 1 + state has been observed and a limit of T 1 / 2 2 ν ( Se 82 , 0 g s + → 0 1 + ) > 1.3 × 10 21 y at 90% CL has been set. Concerning the 0 ν β β decay to the 0 1 + state, a limit for this decay has been obtained with T 1 / 2 0 ν ( Se 82 , 0 g s + → 0 1 + ) > 2.3 × 10 22 y at 90% CL, independently from the 2 ν β β decay process. These results are obtained for the first time with a tracko-calo detector, reconstructing every particle in the final state.