GERmanium Detector Array

The Germanium Detector Array (or GERDA) experiment was searching for neutrinoless double beta decay (0) in Ge-76 at the underground Laboratori Nazionali del Gran Sasso (LNGS). Neutrinoless beta decay is expected to be a very rare process if it occurs. The collaboration predicted less than one event each year per kilogram of material, appearing as a narrow spike around the 0 Q-value (Q = 2039 keV) in the observed energy spectrum. This meant background shielding was required to detect any rare decays. The LNGS facility has 1400 meters of rock overburden, equivalent to 3000 meters of water shielding, reducing cosmic radiation background. The GERDA experiment was operated from 2011 onwards at LNGS. After completing the GERDA experiment, the GERDA collaboration merged with MAJORANA-collaboration to build a new experiment LEGEND. GERDA reported its final results in December 2020 in the Physical Review Letters. The experiment reached all the goals that it set to itself, but no detection of any 0 events was made. The experience from GERDA led to the expectation that further background reduction was in reach so that a background-free experiment with an even larger source strength, respectively exposure, became possible. The LEGEND collaboration, continuing GERDA's work, was aiming at increasing the sensitivity to the half-life of 0 decay up to

Observatory data from Wikidata (CC0). Summary from Wikipedia (CC BY-SA).