Search for EC and ECEC processes in 74Se

Abstract

For the first time, limits on double-beta processes in 74 Se have been obtained using a 400 cm 3 HPGe detector and an external source consisting of natural selenium powder. At a confidence level of 90%, they are 1.9 × 10 18 y for the β + EC(0ν + 2ν) transition to the ground state, 7.7 × 10 18 y for the ECEC(2ν) transition to the 2 + 1 excited state in 74 Ge (595.8 keV), 1.1 × 10 19 y for the ECEC(0ν) transition to the 2 + 1 excited state in 74 Ge (595.8 keV) and 5.5 × 10 18 y for the ECEC(2ν) and ECEC(0ν) transitions to the 2 + 2 excited state in 74 Ge (1204.2 keV). The last transition is discussed in association with a possible enhancement of the decay rate, in this case by several orders of magnitude, because the ECEC(0ν) process is nearly degenerate with an excited state in the daughter nuclide. Prospects for investigating such processes in future experiments are discussed. 14.80.Mz PACS

Average and recommended half-life values for two-neutrino double-beta decay: Upgrade ’05

“…Furthermore, the error presented in [5] appears to be too small, especially taking into account the fact that the signal-to-background ratio in this experiment is equal to ≈ 1/10. It has been mentioned before [40] that the half-life value in this work can be ≈ 1.5-2 times higher because the thickness of the dead layer in the Ge(Li) detectors used can be different for crystals made from enriched Ge, rather than from natural Ge. With no uniformity of the external background, this effect can have appreciable influence on the final result.…”

Nuclear matrix elements for neutrinoless double-beta decay and double-electron capture

“…However, following recent theoretical analysis [3] none of these resonant 0νECEC transitions is favored in the case of light neutrino mass mechanism. The ground state of 74 Se is almost degenerate to the second excited state at 1204 keV in the daughter nucleus 74 Ge, which is a 2 + state [78] and is disfavored by the selection rule [3]. The TGV experiment situated in Modane established limit on the 0νECEC half-life of 1.1 × 10 20 years [76].…”

Evaluation of the resonance enhancement effect in neutrinoless double-electron capture in152Gd,164Er, and180Fang1, Blaum2, Eliseev3 et al. 2012Phys. Rev. C210270View full textAdd to dashboardCite

“…In recent years, experimental searches for the capture process were continued [24][25][26][27][28][29][30] The transition of 106 Cd to an excited state of 106 Pd with the nuclear excitation energy of 2717.59 keV was examined in detail in Ref. [31] for J f = 0.…”