NEXT (Neutrino Experiment with a Xenon TPC) is a neutrinoless double-beta decay experiment that will operate at the Canfranc Underground Laboratory (LSC). It is based on a novel detection concept for neutrinoless double-beta decay searches consisting in a Time Projection Chamber (TPC) filled with high-pressure gaseous xenon and with separated-function capabilities for calorimetry and tracking.
In neutrinoless double beta decay searches, two ingredients have crucial importance: energy resolution and background suppression. The ββ0ν signal is a peak at the endpoint of the ββ2ν energy spectrum (Qββ). On one hand, a higher energy resolution excludes more events with energies close to (but different from) Qββ. On the other hand, due to the large half-life of the searched decay, an optimal background identification is mandatory in order to reject events whose energy falls inside the energy window, to the greatest extent possible.
NEXT offers excellent performance in both aspects: an energy resolution of at least 1% FWHM at Qββ and a topological signature that provides an extra handle in background rejection.
Why choosing xenon? Among the noble gases, xenon is the only one which has an isotope that decays ββ (Xe136), whose natural abundance is quite high (9%) and can be easily enriched by centrifugation. Also, its Qββ value is acceptably high (~ 2458 keV), so that most of background is left outside the region of interest.
The most recent status of NEXT can be found in the latest papers and talks.