Double-beta decay of $$^{130}\hbox {Te}$$ to the first $$0^+$$ excited state of $$^{130}\hbox {Xe}$$ with CUORE-0

We report on a search for double beta decay of $$^{130}\hbox {Te}$$ 130 Te to the first $$0^{+}$$ 0 + excited state of $$^{130}\hbox {Xe}$$ 130 Xe using a $$9.8\,\hbox {kg}\cdot \hbox {yr}$$ 9.8 kg · yr exposure of $$^{130}\hbox {Te}$$ 130 Te collected with the CUORE-0 experiment. In this work we exploit different topologies of coincident events to search for both the neutrinoless and two-neutrino double beta decay modes. We find no evidence for either mode and place lower bounds on the half-lives: $$T^{0\nu }_{0^+_1}>7.9\cdot 10^{23}\hbox {yr}$$ T 0 1 + 0 ν > 7.9 · 10 23 yr and $$T^{2\nu }_{0^+_1}>2.4\cdot 10^{23}\hbox {yr}$$ T 0 1 + 2 ν > 2.4 · 10 23 yr ( $$90\%\,\hbox {CL}$$ 90 % CL ). Combining our results with those obtained by the CUORICINO experiment, we achieve the most stringent constraints available for these processes: $$T^{0\nu }_{0^+_1}>1.4\cdot 10^{24}\hbox {yr}$$ T 0 1 + 0 ν > 1.4 · 10 24 yr and $$T^{2\nu }_{0^+_1}>2.5\cdot 10^{23}\hbox {yr}$$ T 0 1 + 2 ν > 2.5 · 10 23 yr ( $$90\%\,\hbox {CL}$$ 90 % CL ).