Searches for the β⁺ / EC decays of ⁶⁴Zn and ¹¹²Sn, and the ββ decay transitions of ¹²⁴Sn to the excited states of ¹²⁴Te

Results of searches for the β⁺ / EC decays of ⁶⁴Zn and ¹¹²Sn, and the ββ decay of ¹²⁴Sn to excited states in ¹²⁴Te are presented. This work was done at the ChyungPyung Underground Laboratory. An ultra-low background HPGe detector with/without CsI(Tℓ) crystal was used for gamma tagging. No evidence of any of these decay modes has been found. Lower limits on the half-lives on the ¹²⁴Sn decay to different excited channels of ββ decay are set in the range of 10¹⁸ - 10¹⁹ years by 90% C.L. Lower limits of the half-lives of β⁺ / EC decay of ⁶⁴Zn, ¹¹²Sn are obtained to be 9.1 × 10¹⁷ years and 1.3 × 10²⁰ years by 90% C.L., respectively.