An improved limit on the neutrinoless double-electron capture of 36 Ar with GERDA

Agostini, M.; Alexander, A.; Araujo, G. R.; Bakalyarov, A. M.; Balata, M.; Barabanov, I.; Baudis, L.; Bauer, C.; Belogurov, S.; Bettini, A.; Bezrukov, L.; Biancacci, V.; Bossio, E.; Bothe, V.; Brudanin, V.; Brugnera, R.; Caldwell, A.; Cattadori, C.; Chernogorov, A.; Comellato, T.; D’Andrea, V.; Demidova, E. V.; Marco, N. Di; Doroshkevich, E.; Fischer, F.; Fomina, M.; Gangapshev, A.; Garfagnini, A.; Gooch, C.; Grabmayr, P.; Gurentsov, V.; Gusev, K.; Hakenmüller, J.; Hemmer, S.; Hofmann, W.; Huang, J.; Hult, M.; Inzhechik, L. V.; Csáthy, J. Janicskó; Jochum, J.; Junker, M.; Kazalov, V.; Kermaïdic, Y.; Khushbakht, H.; Kihm, T.; Kilgus, K.; Kirpichnikov, I. V.; Klimenko, A.; Kneißl, R.; Knöpfle, K. T.; Kochetov, O.; Kornoukhov, V. N.; Korošec, M.; Krause, P.; Kuzminov, V. V.; Laubenstein, M.; Lindner, M.; Lippi, I.; Lubashevskiy, A.; Lubsandorzhiev, B.; Lutter, G.; Macolino, C.; Majorovits, B.; Maneschg, W.; Manzanillas, L.; Marshall, G.; Misiaszek, M.; Morella, M.; Müller, Y.; Nemchenok, I.; Pandola, L.; Pelczar, K.; Pertoldi, L.; Piseri, P.; Pullia, A.; Ransom, C.; Rauscher, L.; Redchuk, M.; Riboldi, S.; Rumyantseva, N.; Sada, C.; Salamida, F.; Schönert, S.; Schreiner, J.; Schütt, M.; Schütz, A. -K.; Schulz, O.; Schwarz, M.; Schwingenheuer, B.; Selivanenko, O.; Shevchik, E.; Shirchenko, M.; Shtembari, L.; Simgen, H.; Smolnikov, A.; Stukov, D.; Vasenko, A. A.; Veresnikova, A.; Vignoli, C.; Sturm, K. von; Wester, T.; Wiesinger, C.; Wojcik, M.; Yanovich, E.; Zatschler, B.; Zhitnikov, I.; Zhukov, S. V.; Zinatulina, D.; Zschocke, A.; Zsigmond, A. J.; Zuber, K.; Zuzel, G.

doi:10.1140/epjc/s10052-023-12280-6

Unlabelled: The GERmanium Detector Array (Gerda) experiment operated enriched high-purity germanium detectors in a liquid argon cryostat, which contains 0.33% of 36Ar, a candidate isotope for the two-neutrino double-electron capture (2νECEC) and therefore for the neutrinoless double-electron capture (0νECEC). If detected, this process would give evidence of lepton number violation and the Majorana nature of neutrinos. In the radiative 0νECEC of 36Ar, 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 36Ar 0νECEC 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 T1/2>1.5·1022 year. Supplementary information: The online version contains supplementary material available at 10.1140/epjc/s10052-023-12280-6.