The LAr Veto for LEGEND

The LEGEND collaboration is pursuing a tonne-scale ⁷⁶Ge neutrinoless double-beta decay (0νββ) experiment with discovery potential at a half-life approaching or at 1028 years. Observation of 0νββ would violate lepton number conservation, establish the Majorana nature of neutrinos, and serve as an indirect probe of the absolute neutrino mass. LEGEND will build on the successes of the current generation of ⁷⁶Ge 0νββ experiments, GERDA and the MAJORANA DEMONSTRATOR, to limit the background to the level of ∼0.1 counts/FWHM/t/yr. Central to the background suppression is an active liquid argon (LAr) veto, which effectively tags Compton scatters, but introduces an additional background from ⁴²Ar-chain decays. In this talk I will discuss the LEGEND phased experimental concept with particular emphasis on the LAr veto, our associated background budget, and the potential benefit of using

underground argon.

This presentation was used for the Low-Radioactivity Underground Argon Workshop held at Pacific Northwest National Laboratory in Richland, Washington on March 19 - 20, 2018.