nEXO Overview:


Conceptual design of nEXO detector at SNOLAB

nEXO is the multi-ton successor to EXO-200, which will search for neutrinoless double beta decay (0vbb) with substantially improved sensitivity (see the EXO-200 page for more details about why we’re searching for double beta decay). nEXO will be able to observe neutrinoless double beta decay if it occurs with a half life below ~1028 years.

Neutrino oscillation experiments allow us to constrain the differences between the neutrino masses, but two possible orderings of these masses are consistent with these experiments.  If the mass ordering is “inverted” and light Majorana neutrinos mediate 0vbb, then nEXO will have enough sensitivity to observe this decay!  If the mass ordering is “normal,” there is also a significant possibility to discover 0vbb as we increase the half-life sensitivity over existing experiments by more than two orders of magnitude.  Due to this sensitivity, there is substantial possibility that these next-generation searches for 0vbb will directly observe physics beyond the Standard Model in the lab in the coming decade.

The nEXO project has now begun, and our group is working on the design for the photodetector system (~4.5 m2 of silicon photomultipliers), as well as simulation of light and charge collection in the detector. Students interested in these experiments can become involved both in hardware and simulation as the nEXO detector is designed and built.

Additional information:

nEXO public site
Recent publications

kTon Xe detector:


Allowed parameter space for 0vbb in the normal hierarchy

While nEXO has substantial discovery potential for 0vbb, if it does not observe the decay then a detector with sensitivity to half-lives as long as 1030 years may ultimately be required to probe the majority of the remaining parameter space for the decay. Xenon time projection chambers may provide a path to these extremely large detectors (with kton yr exposures), if the required xenon can be acquired. Existing supply chains limit the world’s Xe production to 50–100 t/yr. We are collaborating with LLNL to investigate direct air capture of Xe to determine if acquisition of kton quantities of Xe is possible. More details about ideas for acquiring Xe along with detector concepts reaching 1030 year sensitivity are described here.