First LEGEND-200 Neutrinoless Double-β Decay Results Published in Physical Review Letters
We are pleased to announce the publication of the first physics results from the LEGEND-200 experiment in Physical Review Letters: First Results on the Search for Lepton Number Violating Neutrinoless Double Beta Decay with the LEGEND-200 Experiment (link).
The LEGEND collaboration has published its first results in Physical Review Letters in the search for neutrinoless double-beta (0νββ) decay of ⁷⁶Ge, a major step in determining whether neutrinos are their own antiparticles (i.e. Majorana particles). Observing this hypothetical process, which violates lepton number conservation by two units, would support mechanisms such as leptogenesis, which could explain the matter–antimatter asymmetry observed in the Universe.
The analysis combines data from the GERDA, MAJORANA DEMONSTRATOR, and LEGEND-200, with the latter contributing 61.0 kg·yr of exposure. No signal was observed, resulting in a new limit on the 76Ge 0νββ decay half-life of T1/2>1.9 × 1026 yr (90% C.L.), reaching a world-leading sensitivity of 2.8 x 1026 yr. This corresponds to an upper limit on the effective Majorana neutrino mass of mββ<75–200 meV, depending on the selected nuclear matrix element.
With these first results, LEGEND-200 has demonstrated excellent performance of 142 kg of ⁷⁶Ge-enriched diodes, providing crucial experience for the final phase, LEGEND-1000.