We report a measurement of the half-life of the ${}^{136}\mathrm{Xe}$ two-neutrino double-$\beta$ decay performed with a novel direct-background-subtraction technique. The analysis relies on the data collected with the NEXT-White detector operated with ${}^{136}\mathrm{Xe}$-enriched and ${}^{136}\mathrm{Xe}$-depleted xenon, as well as on the topology of double-electron tracks. With a fiducial mass of only 3.5 kg of Xe, a half-life of $2.{34}_{-0.46}^{+0.80}{\text{(stat)}}_{-0.17}^{+0.30}\text{(sys)}\times {10}^{21}\text{yr}$ is derived from the background-subtracted energy spectrum. The presented technique demonstrates the feasibility of unique background-model-independent neutrinoless double-$\beta$-decay searches.

• Received 25 November 2021
• Revised 25 January 2022
• Accepted 6 April 2022

DOI:https://doi.org/10.1103/PhysRevC.105.055501