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

Abstract

The NEMO-3 results for the double-β decay of 150Nd to the 0+ 1 and 2+ 1 excited states of 150Sm are reported. The data recorded during 5.25 year with 36.6 g of the isotope 150Nd are used in the analysis. The signal of the 2νββ transition to the 0+ 1 excited state is detected with a statistical significance exceeding 5σ. The half-life is measured to be T 2νββ 1/2 (0+ 1 ) = 1.11+0.19 −0.14 (stat) +0.17 −0.15 (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 2νββ decay to the 2+ 1 level the limit is T 2νββ 1/2 (2+ 1 ) > 2.42 × 1020 year. The limits on the 0νββ decay to the 0+ 1 and 2+ 1 levels of 150Sm are significantly improved to T 0νββ 1/2 (0+ 1 ) > 1.36×1022 year and T 0νββ 1/2 (2+ 1 ) > 1.26 × 1022 year.