Measurement of double beta decay of 100Mo to excited states in the NEMO 3 experiment

The double beta decay of Mo-100 to the 0(1)(+) and 2(1)(+) excited states of Ru-100 is studied using the NEMO 3 data. After the analysis of 8024 h of data the half-life for the two-neutrino double beta decay of Mo-100 to the excited 0(1)(+) state is measured to be T-1/2((2v))=[5.7(-0.9)(+1.3)(stat.) +/- 0.8(syst.)] x 10(20) y. The signal -to-background ratio is equal to 3. Information about energy and angular distributions of emitted electrons is also obtained. No evidence for neutrinoless double beta decay to the excited 0(1)(+) state has been found. The corresponding half-life limit is T-1/2((Ov)) (0(+)-> 0(1)(+)) > 8.9 X 10(22) y (at 90% C.L.). The search for the double, beta decay to the 2(1)(+) excited state has allowed the determination of limits on the half-life for the two neutrino mode T-1/2((2v)) (0(+)-> 2(1)(+)) > 1.1 x 10(21) y (at 90% C.L.) and for the neutrinoless mode T-1/2((OV)) (0(+)-> 2(1)(+)) > 1.6 x 10(23) y (at 90% C.L.). (c) 2006 Elsevier B.V. All rights reserved.