Results of a Search for Neutrinoless Double-Βdecay Using the COBRA Demonstrator

Neutrinoless double-$\ensuremath{\beta}$ decay ($0\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$ 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 $^{114}\mathrm{Cd},\phantom{\rule{0.16em}{0ex}}^{128}\mathrm{Te},\phantom{\rule{0.16em}{0ex}}^{70}\mathrm{Zn},\phantom{\rule{0.16em}{0ex}}^{130}\mathrm{Te}$, and $^{116}\mathrm{Cd}$. A Bayesian analysis is performed to estimate the signal strength of $0\ensuremath{\nu}\ensuremath{\beta}\ensuremath{\beta}$ decay. No signal is observed for any of these nuclides. Therefore, the following half-life limits at 90% credibility are set: ${T}_{1/2}^{0\ensuremath{\nu}}g1.6\ifmmode\times\else\texttimes\fi{}{10}^{21}\phantom{\rule{4pt}{0ex}}\mathrm{yr} (^{114}\mathrm{Cd}),\phantom{\rule{0.16em}{0ex}}{T}_{1/2}^{0\ensuremath{\nu}}g1.9\ifmmode\times\else\texttimes\fi{}{10}^{21}\phantom{\rule{4pt}{0ex}}\mathrm{yr} (^{128}\mathrm{Te}),\phantom{\rule{0.16em}{0ex}}{T}_{1/2}^{0\ensuremath{\nu}}g6.8\ifmmode\times\else\texttimes\fi{}{10}^{18}\phantom{\rule{4pt}{0ex}}\mathrm{yr} (^{70}\mathrm{Zn}),\phantom{\rule{0.16em}{0ex}}{T}_{1/2}^{0\ensuremath{\nu}}g6.1\ifmmode\times\else\texttimes\fi{}{10}^{21}\phantom{\rule{4pt}{0ex}}\mathrm{yr} (^{130}\mathrm{Te})$, and ${T}_{1/2}^{0\ensuremath{\nu}}g1.1\ifmmode\times\else\texttimes\fi{}{10}^{21}\phantom{\rule{4pt}{0ex}}\mathrm{yr} (^{116}\mathrm{Cd})$.