2 νββ decay of 76 Ge into excited states with Gerda Phase I 2

Two neutrino double beta decay of 76Ge to excited states of 76Se has been studied using data from Phase I of the GERDA experiment. An array composed of up to 14 germanium detectors including detectors that have been isotopically enriched in 76Ge was deployed in liquid argon. The analysis of various possible transitions to excited final states is based on coincidence events between pairs of detectors where a de-excitation γ ray is detected in one detector and the two electrons in the other. No signal has been observed and an event counting profile likelihood analysis has been used to determine Frequentist 90 DOI: https://doi.org/10.1088/0954-3899/42/11/115201 Posted at the Zurich Open Repository and Archive, University of Zurich ZORA URL: https://doi.org/10.5167/uzh-122053 Accepted Version Originally published at: GERDA Collaboration; Agostini, M; Allardt, M; Bakalyarov, A M; Baudis, L; Benato, G; Walter, M; et al (2015). 2νββ decay of 76Ge into excited states with GERDA Phase I. Journal of Physics G: Nuclear and Particle Physics, 42(11):115201-115218. DOI: https://doi.org/10.1088/0954-3899/42/11/115201 2νββ decay of Ge into excited states with Gerda Phase I Gerda Collaboration‡ M. Agostini, M. Allardt, A.M. Bakalyarov, M. Balata, I. Barabanov, N. Barros§, L. Baudis, C. Bauer, N. Becerici-Schmidt, E. Bellotti, S. Belogurov, S.T. Belyaev, G. Benato, A. Bettini, L. Bezrukov, T. Bode, D. Borowicz, V. Brudanin, R. Brugnera, D. Budjáš, A. Caldwell, C. Cattadori, A. Chernogorov, V. D’Andrea, E.V. Demidova, A. di Vacri, A. Domula, E. Doroshkevich, V. Egorov, R. Falkenstein, O. Fedorova, K. Freund, N. Frodyma, A. Gangapshev, A. Garfagnini, C. Gooch, P. Grabmayr, V. Gurentsov, K. Gusev, A. Hegai, M. Heisel, S. Hemmer, G. Heusser, W. Hofmann, M. Hult, L.V. Inzhechik‖, J. Janicskó Csáthy, J. Jochum, M. Junker, V. Kazalov, T. Kihm, I.V. Kirpichnikov, A. Kirsch, A. Klimenko¶, K.T. Knöpfle, O. Kochetov, V.N. Kornoukhov, V.V. Kuzminov, M. Laubenstein, A. Lazzaro, V.I. Lebedev, B. Lehnert, H.Y. Liao, M. Lindner, I. Lippi, A. Lubashevskiy, B. Lubsandorzhiev, G. Lutter, C. Macolino, B. Majorovits, W. Maneschg, E. Medinaceli, Y. Mi, M. Misiaszek, P. Moseev, I. Nemchenok, D. Palioselitis, K. Panas, L. Pandola, K. Pelczar, A. Pullia, S. Riboldi, N. Rumyantseva, C. Sada, M. Salathe, C. Schmitt, B. Schneider, J. Schreiner, O. Schulz, B. Schwingenheuer, S. Schönert, A-K. Schütz, O. Selivanenko, M. Shirchenko, H. Simgen, A. Smolnikov, L. Stanco, M. Stepaniuk, C.A. Ur, L. Vanhoefer, A.A. Vasenko, A. Veresnikova, K. von Sturm, V. Wagner, M. Walter, A. Wegmann, ‡ LNGS, Assergi, Italy; correspondence: gerda-eb@mpi-hd.mpg.de § present address: Dept. of Physics and Astronomy, Univ. of Pennsylvania, Philadelphia, Pennsylvania, USA ‖ also at: Moscow Inst. of Physics and Technology, Russia ¶ also at: Int. Univ. for Nature, Society and Man “Dubna”, Dubna, Russia ar X iv :1 50 6. 03 12 0v 1 [ he pex ] 9 J un 2 01 5 2νββ decay of Ge into excited states with Gerda Phase I 2 T. Wester, H. Wilsenach, M. Wojcik, E. Yanovich, P. Zavarise, I. Zhitnikov, S.V. Zhukov, D. Zinatulina, K. Zuber, and G. Zuzel. 1 INFN Laboratori Nazionali del Gran Sasso and Gran Sasso Science Institute, Assergi, Italy 2 INFN Laboratori Nazionali del Sud, Catania, Italy 3 Institute of Physics, Jagiellonian University, Cracow, Poland 4 Institut für Kernund Teilchenphysik, Technische Universität Dresden, Dresden, Germany 5 Joint Institute for Nuclear Research, Dubna, Russia 6 Institute for Reference Materials and Measurements, Geel, Belgium 7 Max-Planck-Institut für Kernphysik, Heidelberg, Germany 8 Dipartimento di Fisica, Università Milano Bicocca, Milano, Italy 9 INFN Milano Bicocca, Milano, Italy 10 Dipartimento di Fisica, Università degli Studi di Milano e INFN Milano, Milano, Italy 11 Institute for Nuclear Research of the Russian Academy of Sciences, Moscow, Russia 12 Institute for Theoretical and Experimental Physics, Moscow, Russia 13 National Research Centre “Kurchatov Institute”, Moscow, Russia 14 Max-Planck-Institut für Physik, München, Germany 15 Physik Department and Excellence Cluster Universe, Technische Universität München, Germany 16 Dipartimento di Fisica e Astronomia dell‘Università di Padova, Padova, Italy 17 INFN Padova, Padova, Italy 18 Physikalisches Institut, Eberhard Karls Universität Tübingen, Tübingen, Germany 19 Physik Institut der Universität Zürich, Zürich, Switzerland Abstract. Two neutrino double beta decay of Ge to excited states of Se has been studied using data from Phase I of the Gerda experiment. An array composed of up to 14 germanium detectors including detectors that have been isotopically enriched in Ge was deployed in liquid argon. The analysis of various possible transitions to excited final states is based on coincidence events between pairs of detectors where a de-excitation γ ray is detected in one detector and the two electrons in the other. No signal has been observed and an event counting profile likelihood analysis has been used to determine Frequentist 90 % C.L. bounds for three transitions: 0g.s. − 21 : T 2ν 1/2> 1.6·10 23 yr, 0g.s. − 01 : T 2ν 1/2> 3.7·10 23 yr and 0g.s. − 22 : T 2ν 1/2> 2.3·10 23 yr. These bounds are more than two orders of magnitude larger than those reported previously. Bayesian 90 % credibility bounds were extracted and used to exclude several models for the 0g.s. − 01 transition. Two neutrino double beta decay of Ge to excited states of Se has been studied using data from Phase I of the Gerda experiment. An array composed of up to 14 germanium detectors including detectors that have been isotopically enriched in Ge was deployed in liquid argon. The analysis of various possible transitions to excited final states is based on coincidence events between pairs of detectors where a de-excitation γ ray is detected in one detector and the two electrons in the other. No signal has been observed and an event counting profile likelihood analysis has been used to determine Frequentist 90 % C.L. bounds for three transitions: 0g.s. − 21 : T 2ν 1/2> 1.6·10 23 yr, 0g.s. − 01 : T 2ν 1/2> 3.7·10 23 yr and 0g.s. − 22 : T 2ν 1/2> 2.3·10 23 yr. These bounds are more than two orders of magnitude larger than those reported previously. Bayesian 90 % credibility bounds were extracted and used to exclude several models for the 0g.s. − 01 transition. PACS numbers: 23.40.-s, 21.10.Tg, 27.50.+e, 29.40.Wk