Physics Colloquium - Searching for Lepton Number Violation with a Liquid Xenon TPC

The discovery that neutrinos have nonzero, but inexplicably small, masses hints that these particles may hold a key to physics beyond the Standard Model. In this talk, I will discuss the search for neutrinoless double beta decay (0νββ), a proposed form of radioactive decay which is only possible if neutrinos and antineutrinos are their own antiparticles. A discovery of 0νββ would immediately demonstrate new physics, specifically establishing a) violation of lepton number conservation, b) the generation of mass by a mechanism other than the Higgs, and c) possible connections between neutrino interactions and the dominance of matter over antimatter in the universe. I will describe a proposed next-generation experiment called nEXO, which will search for 0νββ using a liquid xenon time projection chamber (TPC). nEXO is designed to achieve sensitivities more than an order of magnitude beyond the reach of current experiments, which requires the ability to detect just one 0νββ decay event per year in a volume of ~10^28 atoms. We will discuss how the TPC technology will enable nEXO to achieve this exquisite sensitivity, then discuss how its unique capabilities may enable other science in the field of particle astrophysics. I will close with a brief discussion on scaling up the techniques used by nEXO to enable beyond-the-next-generation searches for new physics.