Neutrinoless double-β decay (0νββ 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 Cd114,Te128,Zn70,Te130, and Cd116. A Bayesian analysis is performed to estimate the signal strength of 0νββ decay. No signal is observed for any of these nuclides. Therefore, the following half-life limits at 90% credibility are set: T1/20ν>1.6×1021yr (Cd114),T1/20ν>1.9×1021yr (Te128),T1/20ν>6.8×1018yr (Zn70),T1/20ν>6.1×1021yr (Te130), and T1/20ν>1.1×1021yr (Cd116).
Bibliographical noteFunding Information:
We thank the LNGS for the continuous support of the COBRA experiment, and the AMANDA Collaboration, especially R. Wischnewski, for providing us with their FADCs. We acknowledge the CTU Prague and the ECAP, Erlangen, for valuable discussions. COBRA is supported by the German Research Foundation DFG (Grants No. Zu123/3 and No. GO1133/1).
© 2016 American Physical Society.