Present and Future of 0ν2β Searches with Germanium

Abstract

Among the several experiments and techniques conceived of to search for neutrinoless double β decay (0ν2β) in a handful of isotopes, presently the best lower limit on the half-life for this rare process, is provided by those using 76Ge, a rare isotope of germanium. Such a lower limit is of 1.8 × 1026 y. Building from such a successful achievement of the GERDA and Majorana Demonstrator experiments, the baton with 76Ge passes now to the LEGEND experiment. Using a two-stage approach with about 200 kg and then 1 t of germanium, LEGEND aims to attain a sensitivity of around 1028 y, which will enable it to probe the standard inverted-ordering neutrino mass scenario. We touch upon the past generation of experiments to illustrate their strong and weak points, review the general concept and design of LEGEND, and describe the LEGEND-200 detector and its preliminary performance. We also illustrate how the backgrounds can have a dramatic effect on the search and in which way the latter can be mitigated.