Neutrinoless double-beta decay is a nuclear decay, given as (A,Z) --> (A,Z+2)+2e-, that violates total lepton number conservation by two units. Its observation would have deep consequences in the understanding of our Universe. It would prove that neutrinos have a Majorana component, it would help to understand the origin of the neutrino mass and constrain its absolute mass and help to understand the matter-antimatter asymmetry in the Universe. Due to this very reach scientific harvest, a strong experimental program is underway to search for this transition with many proposed experiments using different technologies.
In the talk the LEGEND experiment, which uses 76Ge as the isotope of interest, will be described. We will start describing its first stage, LEGEND-200, which is now taking data at the Laboratori Nazionali del Gran Sasso of INFN in Italy, and then the status of the future final step, LEGEND-1000.
The goal of LEGEND-200 is to reach a sensitivity in the half-life of the neutrinoless double-beta decay of 76Ge of about 10^27 yr in terms of both setting a 90% C.L. limit and achieving a 50% chance to make a 3 sigma discovery, thanks to a projected background index of 0.6 cts/(FWHMtyr) and an exposure of 1 tyr. LEGEND-1000 aims for a sensitivity of beyond 1028 yr by operating 1 tonne of enriched germanium detectors for an exposure of more than 10 tyr at a background index of about 0.025 cts/(FWHMtyr). Thanks to this sensitivity LEGEND-1000 will be able to explore the entire inverted mass ordering region