Results of a search for neutrinoless double-beta decay using the COBRA demonstrator

Joachim Ebert, Daniel Gehre, Claus Goessling, Caren Hagner, Nadine Heidrich, Reiner Klingenberg, Kevin Kroeninger, Christian Nitsch, Christian Oldorf, Thomas Quante, Silke Rajek, Henning Rebber, Katja Rohatsch, Jan Tebruegge, Robert Temminghoff, Robert Theinert, Jan Timm, Bjoern Wonsak, Stefan Zatschler, Kai Zuber

Published 2015-09-14Version 1

Neutrinoless double-beta decay ($0\nu\beta\beta$-decay) is a hypothetical process that can occur if the neutrino is its own antiparticle. The COBRA collaboration operates a demonstrator to search for these decays at the Laboratori Nazionali del Gran Sasso in Italy using CdZnTe semiconductor detectors. The exposure of $234.7\,$kg\,d considered in this analysis was collected between September 2011 and February 2015. The analysis focuses on the decay of the nuclides $^{114}$Cd, $^{128}$Te, $^{70}$Zn, $^{130}$Te and $^{116}$Cd. A Bayesian analysis is performed to estimate the signal strength of $0\nu\beta\beta$-decay. No signal is observed for any of these nuclides. Therefore, the following half-life limits at 90% credibility are set: $T_{1/2}^{0\nu}>1.5\cdot10^{21}\,$y ($^{114}$Cd), $T_{1/2}^{0\nu}>2\cdot10^{21}\,$y ($^{128}Te$), $T_{1/2}^{0\nu}>7.4\cdot10^{18}\,$y ($^{70}$Zn), $T_{1/2}^{0\nu}>6.7\cdot10^{21}\,$y ($^{130}$Te), and $T_{1/2}^{0\nu}>1.2\cdot10^{21}\,$y ($^{116}$Cd).