Deep-underground search for the decay of with an ultra-low-background HPGe detector

R. Cerroni; S. Dell’Oro; A. Formicola; S. Ghislandi; L. Ioannucci; M. Laubenstein; B. Lehnert; S. S. Nagorny; S. Nisi; L. Pagnanini

doi:10.1140/epjc/s10052-023-12087-5

2024 Impact factor 4.8

Particles and Fields

Open Access

Eur. Phys. J. C (2023) 83: 925
https://doi.org/10.1140/epjc/s10052-023-12087-5

Regular Article - Experimental Physics

Deep-underground search for the decay of $^{180 m} Ta$ $^{180\textrm{m}}\text {Ta}$ with an ultra-low-background HPGe detector

R. Cerroni¹, S. Dell’Oro²^,3, A. Formicola⁴, S. Ghislandi¹^,5, L. Ioannucci⁶, M. Laubenstein¹^f, B. Lehnert⁷, S. S. Nagorny⁸^,9, S. Nisi¹ and L. Pagnanini¹^,5^,9

¹ INFN-Laboratori Nazionali del Gran Sasso, 67100, Assergi, L’Aquila, Italy
² Università di Milano-Bicocca, 20126, Milan, Italy
³ INFN-Sezione di Milano-Bicocca, 20126, Milan, Italy
⁴ INFN-Sezione di Roma, 00185, Rome, Italy
⁵ Gran Sasso Science Institute, 67100, L’Aquila, Italy
⁶ INFN-Laboratori Nazionali di Frascati, 00044, Frascati, Rome, Italy
⁷ Nuclear Science Division, Lawrence Berkeley National Laboratory, 94720, Berkeley, CA, USA
⁸ Arthur B. McDonald Canadian Astroparticle Physics Research Institute, K7L-3N6, Kingston, ON, Canada
⁹ Department of Physics, Enigneering Physics and Astronomy, Queen’s University, K7L-3N6, Kingston, ON, Canada

^f matthias.laubenstein@lngs.infn.it

Received: 6 June 2023
Accepted: 28 September 2023
Published online: 13 October 2023

Abstract

$^{180 m} Ta$ $^{180\textrm{m}}\text {Ta}$ 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 $^{180 m} Ta$ $^{180\textrm{m}}\text {Ta}$ 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 $^{182} Ta$ $^{182}\text {Ta}$ . We observe no signal in the regions of interest and set half-life limits on the process for the two channels EC and $β^{-}$ $\beta ^-$ : $T_{1 / 2, EC} > 1.6 \times 10^{18}$ $T_{1/2,~\textrm{EC}}> 1.6 \times 10^{18}$ year and $T_{1 / 2, β^{-}} > 1.1 \times 10^{18}$ $T_{1/2,~\beta ^-}> 1.1\times 10^{18}$ year (90% C. I.), respectively. We also set the limit on the $γ$ $\gamma$ de-excitation / IC channel: $T_{1 / 2, IC} > 4.1 \times 10^{15}$ $T_{1/2,~\textrm{IC}}> 4.1 \times 10^{15}$ year (90% C. I.). These are, as of now, the most stringent bounds on the decay of $^{180 m} Ta$ $^{180\textrm{m}}\text {Ta}$ worldwide. Finally, we test the hypothetical scenarios of de-excitation of $^{180 m} Ta$ $^{180\textrm{m}}\text {Ta}$ by cosmological Dark Matter and constrain new parameter space for strongly-interacting dark-matter particle with mass up to $10^{5}$ $$10^5$$ GeV.

© The Author(s) 2023

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