Xenon Detectors for Basic and Applied Science.

Double beta decay is a rare nuclear process in which an even-evem isotope decays by emitting two electrons and two neutrinos by a second order process mediated by the weak interaction. Consequently, the associated lifetimes are always very long, (e.g, 2.11 x 10^21 years in the case of the double beta decay of Xenon-136). Indeed, the process exists due to nuclear pairing interaction that favors energetically the even-even isobars over the odd-odd ones.
In 1937 Ettore Majorana demonstrated that all results of beta decay theory remain unchanged if the
neutrino were its own antiparticle, now known as a Majorana particle. In 1939, Wendell H. Furry proposed that
if neutrinos are Majorana particles, then double beta decay can proceed without the emission of any neutrinos, via the process now called neutrino less double beta decay (bb0nu). Conversely, an observation of bb0nu decays would demonstrate the neutrino is its own antiparticle.
Such an observation is very difficult given the long lifetimes of the process (which depend on the neutrino mass itself).
The NEXT program is developing the technology of high-pressure xenon gas chamber with
electroluminescent readout to build detectors capable to push the current state of the art, ultimately improving the current sensitivity to bb0nu process by two orders of magnitude and therefore making possible a discovery if the neutrino is indeed a Majorana particle.
At the same time, the instrumentation technology developed by NEXT can be applied to build a new
type of TOF-PET scanner with the potential to achieve an extremely accurate time-of-flight resolution. Such a scanner, called PETALO could have a dramatic impact in applications such as brain studies, children oncology and full-body PET.