The Large Enriched Germanium Experiment for Neutrinoless double-beta Decay (LEGEND) is a next-generation ⁷⁶Ge-based neutrinoless ββ (0υββ) decay experimental program. The ultimate goal is to operate one ton of high-purity germanium detector (HPGe) enriched in the isotope ⁷⁶Ge in ultra-clean conditions and probe the 0υββ-decay of ⁷⁶Ge at half-lives longer than 10²⁸ years.

The first stage of the experiment (LEGEND-200) is currently in progress at the Gran Sasso National Laboratory (LNGS) in central Italy. LEGEND-200 operates up to 200 kg of enriched HPGe detectors at cryogenic temperatures of 87K in a cryostat containing approximately 60 tons of liquid Argon. The experiment will take data for approximately 5 years and probe the 0υββ-decay of ⁷⁶Ge at half-lifes of up to 10²⁷ years.

The next stage of the experiment (LEGEND-1000) aims to operate 1000 kg of enriched HPGe detectors and is currently in the research & development (R&D) stage. Once operational, the experiment will take data for approximately 10 years and probe the 0υββ-decay of 76Ge at half-lifes of up to 10²⁸ years.

The main experimental challenge is to achieve an ultra-low background. At half-lifes of 10²⁸ years, only around one 0υββ-decay of ⁷⁶Ge is expected per year. In order to identify such a small signal in the presence of naturally occurring radioactive decays, very sophisticated techniques have to be employed. This ranges from the use of extremely clean materials to advanced data analysis methods.

Our research team is involved both in LEGEND-200 and LEGEND-1000, specialising in data analysis and the development and characterisation of ultra-clean readout electronics for HPGe detectors.