The use of enriched liquid Xe-136 (LXe) offers significant advantages to search for double beta decay processes. A discovery of the neutrinoless mode (0vbb) would reveal new properties of neutrinos including first measurement of its mass scale, evidence that they are their own antiparticles, and a first observation of lepton number violation.
The Enriched Xenon Observatory (EXO) employs a time projection chamber filled with LXe to search for 0vbb, which allows an efficient and monolithic detector, ideal to identify and separate background arising from gamma rays. The EXO-200 is a 100-kg class detector in operation at the WIPP mine in New Mexico, USA. Its latest search for 0vbb is among the world’s best, with sensitivity to the 0vbb half-life of 3.7x10^25 yr at the 90% confidence level. To further reject backgrounds, this search introduced a boosted decision tree trained on multiple topological variables. Rooted in the success of EXO-200, nEXO is a tonne-scale detector being designed to reach a sensitivity near 10^28 yr.
In this talk, the latest results with EXO-200 as well as projections for nEXO, the next generation experiment, will be discussed.