LEGEND-1000: A Ton-Scale Search for Neutrinoless Double-Beta Decay in Ge-76*

Next-generation neutrinoless double-beta decay searches seek the Majorana nature of neutrinos and the existence of a lepton number violating process at a decay half-life corresponding to the inverted-ordering neutrino mass scale, assuming the light Majorana neutrino exchange mechanism. The proposed LEGEND-1000 experiment represents the ton-scale phase of the LEGEND program's search for neutrinoless double-beta decay of ⁷⁶Ge, which follows upon the current intermediate-stage LEGEND-200 experiment at LNGS in Italy. The LEGEND-1000 design is centered around a 1000-kg mass of p-type, inverted-coaxial, point-contact germanium detectors operated within a liquid argon active shield. This approach has achieved the lowest background levels and the best energy resolution at the decay Q value among the existing technologies as established by the GERDA and MAJORANA DEMONSTRATOR experiments. The LEGEND-1000 experiment's technical design, energy resolution, material selection, and background suppression techniques combine to project a background-free search for neutrinoless double-beta decay in ⁷⁶Ge at a half-life beyond 10²⁸ yr and a discovery sensitivity that covers the inverted-ordering neutrino mass scale. The innovation behind the LEGEND-1000 design, as well as its technical readiness and discovery potential is presented.