Search for $\beta^+$EC and ECEC processes in $^{74}$Se

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 $1.9\times 10^{18}$ y for the $\beta^+$EC$(0\nu + 2\nu)$ transition to the ground state, $7.7\times 10^{18}$ y for the ECEC($2\nu$) transition to the $2^+_1$ excited state in $^{74}$Ge (595.8 keV), $1.1\times 10^{19}$ y for the ECEC($0\nu$) transition to the $2^+_1$ excited state in $^{74}$Ge (595.8 keV) and $5.5\times 10^{18}$ y for the ECEC($2\nu$) and ECEC($0\nu$) 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$(0\nu)$ process is nearly degenerate with an excited state in the daughter nuclide. Prospects for investigating such processes in future experiments are discussed.
Document type :
Conference papers

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Submitted on : Friday, January 26, 2007 - 11:41:13 AM
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Citation

A. S. Barabash, P. Hubert, A. Nachab, V. Umatov. Search for $\beta^+$EC and ECEC processes in $^{74}$Se. 2nd Symposium on "Neutrino and Dark Matter in Nuclear Physics, Sep 2006, Paris, France. ⟨in2p3-00126822⟩

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