Juan José Gómez Cadenas (Donostia International Physics Center and Ikerbasque)
The next generation of neutrinoless double beta decay experiments, aiming to explore lifetimes of 10**27 year and beyond in several bb0nu decaying isotopes is currently being prepared. Given the very long lifetimes to be explored, at least one order of magnitude longer than the current limits, those experiment must aim for large exposures (in the range of tens of ton year) and virtually zero background. This poses an extraordinary challenge to all existing technologies.
The NEXT experiment is developing high pressure xenon chamber TPC’s which offers a combination of mass scalability, good energy resolution, low radioactive budget, and additional handles to suppress backgrounds. In particular, the reconstruction of the topology of the event has been demonstrated by NEXT-White, and very intense R&D is under way to explore the possibility of detecting the Ba++ isotope produced in the decay of Xe-136. In this talk I will describe the current status of the experiment (the NEXT-White detector, currently operating at the Canfranc Underground Laboratory), short prospects (NEXT-100, schedule to start operations in 2020) and medium/ long term plans. Specifically I will discuss NEXT-HD, a ton-scale detector that improves incrementally NEXT-100 and a more aggressive approach, based in the recent successful R&D on barium tagging, NEXT-BOLD, which could be a ton-scale, truly background free detector.