The search for the neutrinoless double-beta decay of certain even-even nuclei is likely to have a significant impact on our understanding of some of the remaining unknown fundamental neutrino characteristics within the next one-to-two decades. Observation of this decay would establish the Majorana nature of the neutrino and set the absolute mass scale of neutrinos. The Enriched Xenon Observatory (EXO) is an experimental program that is aimed at searching for the neutrinoless double beta decay using the Xe-136 isotope. The EXO-200 detector, which has been operational with enriched xenon at the WIPP site for over a year, contains 200 kg of xenon enriched to 80% in Xe-136 in an ultra-low background TPC. I will present recent results, including the first-measurement of the two neutrino double beta decay of Xe-136, as well as the constraints on the neutrinoless mode of the decay. No evidence from this search for a neutrinoless decay has been found: the results are in significant tension with a decade-old claimed observation of this decay (in Ge-76) for most models. Following the success of the ongoing EXO-200 experiment, specifically the realization of the designed background index and energy resolution, I will describe the next phase of the EXO suite of experiments (nEXO), a planned 5 ton enriched liquid xenon detector. I will also briefly cover the broader EXO R&D effort to realize a background-free search.
Coffee and cookies before the presentation at 3:15 pm, and refreshments after the presentation will both be served in Room 128.