https://doi.org/10.1140/epjc/s10052-023-12280-6
Regular Article - Experimental Physics
An improved limit on the neutrinoless double-electron capture of
Ar with 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, Kraków, 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
NRNU MEPhI, Moscow, Russia
23
Duke University, Durham, NC, USA
24
Moscow Institute of Physics and Technology, Moscow, Russia
25
Dubna State University, Dubna, Russia
26
INFN Roma Tre, Rome, Italy
Received:
22
August
2023
Accepted:
21
November
2023
Published online:
14
January
2024
The GERmanium Detector Array (Gerda) experiment operated enriched high-purity germanium detectors in a liquid argon cryostat, which contains 0.33% of Ar, a candidate isotope for the two-neutrino double-electron capture (2
ECEC) and therefore for the neutrinoless double-electron capture (0
ECEC). If detected, this process would give evidence of lepton number violation and the Majorana nature of neutrinos. In the radiative 0
ECEC of
Ar, a monochromatic photon is emitted with an energy of 429.88 keV, which may be detected by the Gerda germanium detectors. We searched for the
Ar 0
ECEC with Gerda data, with a total live time of 4.34 year (3.08 year accumulated during Gerda Phase II and 1.26 year during Gerda Phase I). No signal was found and a 90% CL lower limit on the half-life of this process was established
year.
Supplementary Information The online version contains supplementary material available at https://doi.org/10.1140/epjc/s10052-023-12280-6.
© The Author(s) 2024
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