Background: Excited-state transitions in double-beta decays are a powerful tool to validate and tune calculations of nuclear matrix elements. Purpose: The experimental lower half-life limits for double-beta decays of 110Pd and 102Pd into the excited 2_1^+ and 0_1^+ states are improved. Furthermore, the first limits of transitions into the 2_2^+ , 0_2^+ , and 2_3^+ states are published for 110Pd as well as a first limit for the 2_2^+ state transition in 102Pd. Methods: The Pd sample was measured with two HPGe detectors in sandwich configuration in the HADES underground laboratory during 44.77 d of lifetime. The analysis was performed with the frequentist Feldman-Cousins method. Results: Lower half-life limits of 1.98 × 10^20 and 1.72 × 10^20 yr (95% CL) were found for the first 0^+ and 2^+ excited states in 110Pd, respectively. This is an improvement by more than a factor of 3 with respect to previous measurements. In 102Pd, the lower half-life limit could be improved to 5.95 × 10^18 yr (95% CL) for the first 0^+ excited state. Furthermore, first experimental lower half-life limits were found for all possible excited states in the 110Pd and 102Pd systems. Conclusions: Previous half-life limits were improved and experimental results were obtained for all theoretical calculations of palladium double-beta decays into excited states.

LEHNERT B.;  ZUBER K.;  ANDREOTTI Erica;  HULT Mikael; 

2013-04-30

AMER PHYSICAL SOC

JRC78243

0556-2813,   

http://link.aps.org/doi/10.1103/PhysRevC.87.034312,    https://publications.jrc.ec.europa.eu/repository/handle/JRC78243,   

10.1103/PhysRevC.87.034312,