Abstract
The majorana demonstrator is a neutrinoless double- decay search consisting of a low-background modular array of high-purity germanium detectors, of which are enriched to 88% in . The experiment is also searching for double-beta decay of to excited states (e.s.) in . can decay into three daughter states of , with clear event signatures consisting of a -decay followed by the prompt emission of one or two rays. This results with high probability in multi-detector coincidences. The granularity of the demonstrator detector array enables powerful discrimination of this event signature from backgrounds. Using 41.9 kg yr of isotopic exposure, the demonstrator has set world leading limits for each e.s. decay of , with 90% CL lower half-life limits in the range of yr. In particular, for the transition to the first e.s. of , a lower half-life limit of yr at 90% CL was achieved.
4 More- Received 14 August 2020
- Accepted 2 November 2020
DOI:https://doi.org/10.1103/PhysRevC.103.015501
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