Searching for neutrinoless double beta decay using the nEXO detector*

The observation of neutrinoless double beta decay (0vbb) always implies new physics. The nEXO detector, a 5 ton-scale liquid xenon time projection chamber (TPC) enriched to 90% in the isotope ¹³⁶Xe, plans to observe neutrinoless double beta decay and produce first data in 2030. nEXO consists of a single-phase, monolithic volume of liquid xenon with 1.2 m diameter and 1.2 m long drift space where the dominant gamma backgrounds may be tagged by their Compton scattering topology and are attenuated in the deeper region of the detector. The nEXO detector is designed such that no single component dominates its radioactive background, each low radioactivity material has an identified vendor or source, and a variety of radioactive decays may be directly measured and identified to validate a radioactive background model. Its projected sensitivity is robust against backgrounds and “unknown unknowns” due to the use of multiple observables, including event topology, energy (<1% resolution at the 0vbb Q-value) and distance from any materials in the TPC. These factors result in an estimated 0vbb half-life sensitivity of 1.35 x 10²⁸ year half-life at 90% confidence level after 10 years of exposure time. This talk will provide an overview of nEXO as well as a summary of the diverse range of R&D efforts presently underway.