The NEXT experiment

TL;DR

The NEXT experiment aims to detect neutrinoless double beta decay in Xe136 using advanced TPC technology with excellent energy resolution, background suppression, and scalability, progressing through multiple prototype stages.

Contribution

This paper presents the design, technological advancements, and staged roadmap of the NEXT experiment for neutrinoless double beta decay detection.

Findings

Successful demonstration of HPXE technology with prototypes.

Background characterization and measurement of bb2nu signal.

Progression towards large-scale detectors with enhanced background suppression.

Abstract

NEXT (Neutrino Experiment with a Xenon TPC) is an experiment to search neutrinoless double beta decay processes (bb0nu) in Xe136. 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, which further contributes to the suppression 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 deploying a mass of natural xenon in the range of 1 kg, using the NEXT-DEMO (IFIC) and NEXT-DBDM (Berkeley) prototypes; ii) Characterisation of the backgrounds to the bb0nu signal and measurement of the bb2nu signal with the NEW detector, deploying 10 kg of enriched xenon and operating at the LSC; iii) Search for bb0nu decays with the NEXT-100 detector, which deploys 100 kg of enriched xenon; iv) Search for bb0nu 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).