Grant: Subatomic Physics Envelope - Individual

The Enriched Xenon Observatory (EXO) project aims to measure the double beta decay (2nbb) spectrum of 136Xe for the first time and carry out a sensitive search for neutrinoless double beta decay (0nbb). Discovery of 0nbb will provide new fundamental information on neutrino properties including demonstrating that neutrinos and anti-neutrinos are the same, indicating the neutrino mass scale, and neutrino mass ordering. The 2nbb process is one in which two neutrons in a nucleus simultaneously decay into protons with the concurrent emission of two electrons and two neutrinos. The 0nbb process is similar except that no neutrinos are emitted. The EXO collaboration is developing time projection chamber (TPC) technology to identify and measure the two emitted electrons via the production of ionization and scintillation signals in the detector. A unique spectroscopic laser tagging system is being developed to identify the barium ion created from the decay for background elimination. A 200 kg liquid-phase prototype is being designed and fabricated by the international EXO collaboration and installation at the Waste Isolation Pilot Plant (WIPP) in New Mexico has commenced. The Canadian EXO group is providing substantial contributions to the engineering and design of the detector systems, and installation at WIPP. Gas-phase technology is also being pursued and led by the Canadian EXO researchers. The advantages of a gas-phase detector include the ability to reconstruct tracks for signal identification and background rejection and in-situ spectroscopic barium tagging. The Canadian EXO team will develop the gas phase technology with the mid-term goal to design, fabricate, and operate a 200 kg gas-phase xenon TPC at SNOLAB.