Abstract

If neutrinos were the one (and only) instance of elementary particles of the Majorana type, they could undergo a hypothetical process violating lepton number, the so-called Neutrinoless double-beta decay. If indeed it were observed, that would be enough to claim the Majorana nature of neutrinos. Several experiments have been conceived, which search for this mode in a handful of isotopes, baring a favourable energy-momentum configuration. A variety of experimental techniques are being employed in the quest. So far the best statistical sensitivity on the half-life for the process occurrence is of around 10^{26} yr and belongs to experiments employing Ge76 (germanium) both as source and as semi-conducting detector. It comes from an experiment called GERDA, based at the Italian underground Laboratori Nazionali del Gran Sasso (LNGS). In this seminar I will focus on the child born of GERDA and its US counterpart, the "MAJORANA Demonstrator": LEGEND. Using a two-stage approach with about 200 kg first and then 1000 kg of germanium diodes enriched in Ge76, LEGEND aims to attain a sensitivity around 10^{28} years in half-life, probing the inverted-ordering of the neutrino masses. I will review the general concept and design of LEGEND; describe the detectors and their current performance in the present LEGEND-200 phase, after several months of commissioning and physics data taking at LNGS. I will also illustrate how the backgrounds can have a dramatic effect on the search; and in which way this can be mitigated, with some emphasis on the use of the liquid-argon detector. Finally, I will provide an expected timeline to get LEGEND-1000 up and running and the related R&D activities.