Abstract
We used the reaction to carry out an in-depth study of states in , up to around 2.5 MeV. In this Letter, we place emphasis on hitherto unobserved states below the first level, which are important in the context of solar neutrino and fermionic dark matter (FDM) detection in large-scale xenon-based experiments. We identify for the first time candidate metastable states in , which would allow a real-time detection of solar neutrino and FDM events in xenon detectors, with high background suppression. Our results are also compared with shell-model calculations performed with three Hamiltonians that were previously used to evaluate the nuclear matrix element (NME) for neutrinoless double beta decay. We find that one of these Hamiltonians, which also systematically underestimates the NME compared with the others, dramatically fails to describe the observed low-energy spectrum, while the other two show reasonably good agreement.
- Received 22 January 2023
- Accepted 7 July 2023
DOI:https://doi.org/10.1103/PhysRevLett.131.052501
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