https://doi.org/10.1140/epjc/s10052-023-11862-8
Regular Article - Experimental Physics
Search for tri-nucleon decays of 
Ge in GERDA
1
INFN Laboratori Nazionali del Gran Sasso, Assergi, Italy
2
INFN Laboratori Nazionali del Gran Sasso and Gran Sasso Science Institute, Assergi, Italy
3
INFN Laboratori Nazionali del Gran Sasso and Università degli Studi dell’Aquila, L’Aquila, Italy
4
INFN Laboratori Nazionali del Sud, Catania, Italy
5
Institute of Physics, Jagiellonian University, Cracow, Poland
6
Institut für Kern- und Teilchenphysik, Technische Universität Dresden, Dresden, Germany
7
Joint Institute for Nuclear Research, Dubna, Russia
8
European Commission, JRC-Geel, Geel, Belgium
9
Max-Planck-Institut für Kernphysik, Heidelberg, Germany
10
Department of Physics and Astronomy, University College London, London, UK
11
INFN Milano Bicocca, Milan, Italy
12
Dipartimento di Fisica, Università degli Studi di Milano and INFN Milano, Milan, Italy
13
Institute for Nuclear Research of the Russian Academy of Sciences, Moscow, Russia
14
Institute for Theoretical and Experimental Physics, NRC “Kurchatov Institute”, Moscow, Russia
15
National Research Centre “Kurchatov Institute”, Moscow, Russia
16
Max-Planck-Institut für Physik, Munich, Germany
17
Physik Department, Technische Universität München, Munich, Germany
18
Dipartimento di Fisica e Astronomia, Università degli Studi di Padova, Padua, Italy
19
INFN Padova, Padua, Italy
20
Physikalisches Institut, Eberhard Karls Universität Tübingen, Tübingen, Germany
21
Physik-Institut, Universität Zürich, Zurich, Switzerland
22
Duke University, Durham, NC, USA
23
Leibniz-Institut für Kristallzüchtung, Berlin, Germany
24
NRNU MEPhI, Moscow, Russia
25
Moscow Institute of Physics and Technology, Moscow, Russia
26
Dubna State University, Dubna, Russia
Received:
22
April
2023
Accepted:
25
July
2023
Published online:
4
September
2023
We search for tri-nucleon decays of Ge in the dataset from the GERmanium Detector Array (GERDA) experiment. Decays that populate excited levels of the daughter nucleus above the threshold for particle emission lead to disintegration and are not considered. The ppp-, ppn-, and pnn-decays lead to 
Cu, Zn, and Ga nuclei, respectively. These nuclei are unstable and eventually proceed by the beta decay of Ga to Ge (stable). We search for the Ga decay exploiting the fact that it dominantly populates the 66.7 keV 
Ga state with half-life of 0.5 s. The nnn-decays of Ge that proceed via Ge are also included in our analysis. We find no signal candidate and place a limit on the sum of the decay widths of the inclusive tri-nucleon decays that corresponds to a lower lifetime limit of 1.2
10
yr (90% credible interval). This result improves previous limits for tri-nucleon decays by one to three orders of magnitude.
© The Author(s) 2023
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Funded by SCOAP3. SCOAP3 supports the goals of the International Year of Basic Sciences for Sustainable Development.
