Speaker
Description
NEXT is a staged experimental program aiming at the detection of neutrinoless double beta ($\beta\beta0\nu$) decay in $^{136}$Xe using successive generations of high-pressure gaseous xenon time projection chambers. The collaboration is presently concluding four years of operation of NEXT-White, a radiopure 50-cm diameter and length TPC operated with enriched xenon at 10 bar, at the Laboratorio Subterráneo de Canfranc. NEXT-White has successfully demonstrated the two key features of the technology, namely excellent energy resolution (1% FWHM at the Q-value of the decay) and highly effective topological-based background discrimination and served to provide an independent measurement of the $^{136}$Xe two-neutrino double beta decay half-life. The next stage of the program is NEXT-100, planned for construction in 2022, which will be twice larger than NEXT-White, and operated with 97 kg of enriched xenon at 15 bar, with half-life sensitivity on the scale of $10^{26}$ y. NEXT-100 will be superseded by a tonne-scale detector with a sensitivity of $10^{27}$ y around 2026. Parallel to the incremental increase in TPC size, the collaboration pursues an extensive R&D program to develop the capability of detecting the $^{136}$Ba daughter resulting from $^{136}$Xe double beta decays inside a running TPC using single molecule fluorescence imaging. This effort can lead to a background-free search for $\beta\beta0\nu$ decay on the tonne-scale, with half-life sensitivities close to $10^{28}$ y. This talk will present the status of the program, summarizing our experience with the NEXT-White TPC, provide an overview of the barium-tagging activities, and outline the future steps of the experiment.
