Improved Limit on Neutrinoless Double-Beta Decay in ${}^{130}\hspace{0.17em}\mathrm{Te}$ with CUORE

We report new results from the search for neutrinoless double-beta decay in ${}^{130}\hspace{0.17em}\mathrm{Te}$ with the CUORE detector. This search benefits from a fourfold increase in exposure, lower trigger thresholds, and analysis improvements relative to our previous results. We observe a background of $(1.38\pm 0.07)\times {10}^{-2}\mathrm{counts}/(\mathrm{keV}\mathrm{kg}\mathrm{yr})$) in the $0\nu \beta \beta$ decay region of interest and, with a total exposure of 372.5 kg yr, we attain a median exclusion sensitivity of $1.7\times {10}^{25}\mathrm{yr}$. We find no evidence for $0\nu \beta \beta$ decay and set a 90% credibility interval Bayesian lower limit of $3.2\times {10}^{25}\mathrm{yr}$ on the ${}^{130}\hspace{0.17em}\mathrm{Te}$ half-life for this process. In the hypothesis that $0\nu \beta \beta$ decay is mediated by light Majorana neutrinos, this results in an upper limit on the effective Majorana mass of 75–350 meV, depending on the nuclear matrix elements used.

Figure 1

Exposure collected by CUORE starting from May 2017. The data in gray represent the exposure accumulated at the time of writing, while the data in red are used for the present work (372.5 kg yr).

Figure 2

Distribution of energy thresholds at 90% trigger efficiency for the DT and OT algorithms.

Figure 3

The CUORE spectrum after applying the base cuts to remove heater events and periods affected by baseline or noise instabilities (gray), after the anticoincidence cut (AC) (red), and after the PSA cut (blue).

Figure 4

ROI spectrum with the best-fit curve (solid red) and the best fit-curve with the $0\nu \beta \beta$ decay component fixed to the 90% CI limit (dashed blue).

Figure 5

Posterior on ${\mathrm{\Gamma }}_{0\nu }$ with all systematics included for the fit on the physical range (${\mathrm{\Gamma }}_{0\nu }>0$) and on the full range. The 90% CI is shown in blue.