180 mTa is the longest-lived metastable state presently known. Its decay has not been observed yet. In this work, we report a new result on the decay of 180 mTa obtained with a 2015.12-g tantalum sample measured for 527.7 d with an ultra-low background HPGe detector in the STELLA laboratory of the Laboratori Nazionali del Gran Sasso (LNGS), in Italy. Before the measurement, the sample has been stored deep-underground for ten years, resulting in subdominant background contributions from cosmogenically activated 182Ta . We observe no signal in the regions of interest and set half-life limits on the process for the two channels EC and β- : T1/2,EC>1.6×1018 year and T1/2,β->1.1×1018 year (90% C. I.), respectively. We also set the limit on the γ de-excitation / IC channel: T1/2,IC>4.1×1015 year (90% C. I.). These are, as of now, the most stringent bounds on the decay of 180 mTa worldwide. Finally, we test the hypothetical scenarios of de-excitation of 180 mTa by cosmological Dark Matter and constrain new parameter space for strongly-interacting dark-matter particle with mass up to 10 5 GeV
Cerroni, R., Dell'Oro, S., Formicola, A., Ghislandi, S., Ioannucci, L., Laubenstein, M., et al. (2023). Deep-underground search for the decay of 180 mTa with an ultra-low-background HPGe detector. EUROPEAN PHYSICAL JOURNAL. C, PARTICLES AND FIELDS, 83(10) [10.1140/epjc/s10052-023-12087-5].
Deep-underground search for the decay of 180 mTa with an ultra-low-background HPGe detector
Dell'Oro, S.;Pagnanini, L.
2023
Abstract
180 mTa is the longest-lived metastable state presently known. Its decay has not been observed yet. In this work, we report a new result on the decay of 180 mTa obtained with a 2015.12-g tantalum sample measured for 527.7 d with an ultra-low background HPGe detector in the STELLA laboratory of the Laboratori Nazionali del Gran Sasso (LNGS), in Italy. Before the measurement, the sample has been stored deep-underground for ten years, resulting in subdominant background contributions from cosmogenically activated 182Ta . We observe no signal in the regions of interest and set half-life limits on the process for the two channels EC and β- : T1/2,EC>1.6×1018 year and T1/2,β->1.1×1018 year (90% C. I.), respectively. We also set the limit on the γ de-excitation / IC channel: T1/2,IC>4.1×1015 year (90% C. I.). These are, as of now, the most stringent bounds on the decay of 180 mTa worldwide. Finally, we test the hypothetical scenarios of de-excitation of 180 mTa by cosmological Dark Matter and constrain new parameter space for strongly-interacting dark-matter particle with mass up to 10 5 GeVFile | Dimensione | Formato | |
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