Measurement of the $\beta \beta$ Decay Half-Life of ${}^{130}\mathrm{Te}$ with the NEMO-3 Detector

We report results from the NEMO-3 experiment based on an exposure of 1275 days with 661 g of ${}^{130}\mathrm{Te}$ in the form of enriched and natural tellurium foils. The $\beta \beta$ decay rate of ${}^{130}\mathrm{Te}$ is found to be greater than zero with a significance of 7.7 standard deviations and the half-life is measured to be $T_{1/2}^{2\nu }=[7.0\pm 0.9(\mathrm{stat})\pm 1.1(\mathrm{syst})]\times {10}^{20}\mathrm{yr}$. This represents the most precise measurement of this half-life yet published and the first real-time observation of this decay.

Figure 1

Energy sum distribution for crossing-electron events for (a) ${}^{130}\mathrm{Te}$ and (b) ${}^{\mathrm{nat}}\mathrm{Te}$ (b); Energy distribution of electron events coming from the source foil for (c) ${}^{130}\mathrm{Te}$ and (d) ${}^{\mathrm{nat}}\mathrm{Te}$. Dots correspond to the data and histograms to the fit of the background model.

Figure 2

(a),(b) Distribution of the sum of the electron energies; (c),(d) individual electron energy; and (e),(f) cosine of the angle between the electron tracks for two-electron events selected from the two Te foils: (a),(c),(e) enriched in ${}^{130}\mathrm{Te}$ and (b),(d),(f) natural Te.