Measurement of the ${}^{136}$Xe two-neutrino double beta decay half-life via direct background subtraction in NEXT

We report a measurement of the half-life of the 136 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 Xe-enriched and 136 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 . 80 − 0 . 46 (stat) +0 . 30 − 0 . 17 (sys) × 10 21 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.