Measurement of the double- β decay of 150 Nd to the 0 1+ excited state of 150 Sm in NEMO-3

Abstract

The NEMO-3 results for the double- β decay of 150 Nd to the 0 1+ and 2 1+ excited states of 150 Sm are reported. The data recorded during 5.25 year with 36.6 g of the isotope 150 Nd are used in the analysis. The signal of the 2 νββ transition to the 0 1+ excited state is detected with a statistical significance exceeding 5 σ . The half-life is measured to be T1/22νββ(01+)=[1.11-0.14+0.19(stat)-0.15+0.17(syst)]×1020 year, which is the most precise value that has been measured to date. 90% confidence-level limits are set for the other decay modes. For the 2 νββ decay to the 2 1+ level the limit is T1/22νββ(21+)>2.42×1020year . The limits on the 0 νββ decay to the 0 1+ and 2 1+ levels of 150 Sm are significantly improved to T1/20νββ(01+)>1.36×1022year and T1/20νββ(21+)>1.26×1022year .