Search for exotic physics in double-β decays with GERDA Phase II

Agostini, M.; Alexander, A.; Araujo, G.; Bakalyarov, A. M.; Balata, M.; Barabanov, I.; Baudis, L.; Bauer, C.; Belogurov, S.; Bettini, A.; Bezrukov, L.; Biancacci, V.; Bossio, E.; Bothe, V.; Brugnera, R.; Caldwell, A.; Calgaro, S.; Cattadori, C.; Chernogorov, A.; Comellato, T.; D'Andrea, V.; Demidova, E. V.; Di Giacinto, A.; Di Marco, N.; Doroshkevich, E.; Fischer, F.; Fomina, M.; Gangapshev, A.; Garfagnini, A.; Gooch, C.; Grabmayr, P.; Gurentsov, V.; Gusev, K.; Hakenmuller, J.; Hemmer, S.; Hofmann, W.; Huang, J.; Hult, M.; Inzhechik, L. V.; Janicsko Csathy, J.; Jochum, J.; Junker, M.; Kazalov, V.; Kermaidic, Y.; Khushbakht, H.; Kihm, T.; Kilgus, K.; Kirpichnikov, I. V.; Klimenko, A.; Knopfle, K. T.; Kochetov, O.; Kornoukhov, V. N.; 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.; Miloradovic, M.; Mingazheva, R.; Misiaszek, M.; Morella, M.; Muller, 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.; Sailer, S.; Salamida, F.; Schonert, S.; Schreiner, J.; Schutt, M.; Schutz, 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.; von Sturm, K.; 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:10.1088/1475-7516/2022/12/012

A search for Beyond the Standard Model double-beta decay modes of 76Ge has been performed with data collected during the Phase II of the GERmanium Detector Array (Gerda) experiment, located at the Laboratori Nazionali del Gran Sasso of INFN (Italy). Improved limits on the decays involving Majorons have been obtained, compared to previous experiments with 76Ge, with half-life values on the order of 10^23 yr. For the first time with 76Ge, limits on Lorentz invariance violation effects in double-beta decay have been obtained.The isotropic coefficient °a(3)_of , which embeds Lorentz violation in double-beta decay, has been constrained at the order of 10^(−6) GeV. We also set the first experimental limits on the search for light exotic fermions in double-beta decay, including sterile neutrinos.