https://doi.org/10.1140/epjc/s10052-025-14348-x
Regular Article - Experimental Physics
Improved sensitivity in the search for rare decays of Gd isotopes
1
Technische Universität Dresden, Institut für Kern und Teilchenphysik, Zellescher Weg 19, 01069, Dresden, Germany
2
Gran Sasso Science Institute, viale F. Crispi 7, 67100, L’Aquila, Italy
3
School of Mathematical and Physical Sciences, The University of Sheffield, Hounsfield Road, S3 7RH, Sheffield, UK
4
INFN-Laboratori Nazionali del Gran Sasso, Via G. Acitelli 22, 67100, Assergi, AQ, Italy
5
STFC, Boulby Underground Laboratory, Boulby Mine, TS13 4UZ, Redcar-and-Cleveland, UK
a
bjoern.lehnert@tu-dresden.de
Received:
17
February
2025
Accepted:
22
May
2025
Published online:
14
June
2025
Gadolinium is widely used in multiple low-background experiments, making its isotopes accessible for rare decay searches both in-situ and through radiopurity screening data. This study presents an improved search for rare alpha and double-beta decay modes in 
, 
, and 
isotopes using ultra-low background HPGe detectors at the Boulby Underground Screening (BUGS) facility. A total exposure of 6.7 
of natural gadolinium was achieved using gadolinium sulfate octahydrate 
samples, originally screened for radiopurity prior to their deployment in the Super-Kamiokande neutrino experiment. Due to the detection methodology, only decays into excited states accompanied by gamma-ray emission were accessible. A Bayesian analysis incorporating prior experimental results was employed, leading to new lower half-life limits in the range of 
years - an improvement of approximately two orders of magnitude over previous constraints. No statistically significant decay signals were observed. These results demonstrate the effectiveness of repurposing large-scale radiopurity screening campaigns for fundamental physics research.
© The Author(s) 2025
Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/.
Funded by SCOAP3.
