Nuclear Physics B Proceedings Supplement The NEXT experiment

NEXT (Neutrino Experiment with a Xenon TPC) is an experiment to search neutrinoless double beta decay pro-cesses (ββ0ν). The isotope chosen by NEXT is 136Xe. The NEXT technology is based in the use of time projection chambers operating at a typical pressure of 15 bar and using electroluminescence to amplify the signal (HPXe). The main advantages of the experimental technique are: a) excellent energy resolution; b) the ability to reconstruct the trajectory of the two electrons emitted in the decays, a unique feature of the HPXe which further contributes to the sup-pression of backgrounds; c) scalability to large masses; and d) the possibility to reduce the background to negligible levels thanks to the barium tagging technology (BaTa). The NEXT roadmap was designed in four stages: i) Demonstration of the HPXe technology with prototypes de-ploying a mass of natural xenon in the range of 1 kg; ii) Characterisation of the backgrounds to the ββ0ν signal and measurement of the ββ2ν signal with the NEW detector, deploying 10 kg of enriched xenon and operating at the LSC; iii) Search for ββ0ν decays with the NEXT-100 detector, which deploys 100 kg of enriched xenon; iv) Search for ββ0ν decays with the BEXT detector, which will deploy masses in the range of the ton and will introduce two additional handles, only possible in a HPXe: a) A magnetic field, capable of further enhancing the topological signal of NEXT; and b) barium-tagging (a technique pioneered by the EXO experiment which is also accessible to NEXT)