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The final result of GERDA and the physics potential of LEGEND

Not scheduled
Asynchronous Talk Neutrino Physics Neutrino Physics Session 2


Christoph Wiesinger (Technical University of Munich)


Hidden by their tiny mass, neutrinos may carry a profound secret with far-reaching consequences for both particle physics and cosmology. Given zero electric charge and no color, they may be Majorana particles - fermions which are their own anti-particles. Double beta decay offers a unique probe for this hypothesis. Finding solely two electrons sharing the full available decay energy, would prove lepton number non-conservation and reveal the Majorana character of neutrinos. The superb spectroscopic performance of high-purity germanium detectors provides exceptional discovery potential for the mono-energetic peak and separates it from the standard-model allowed continuum. The Germanium Detector Array (GERDA) experiment has searched for this decay, operating 40 kg of enriched germanium in an instrumented low-background liquid argon environment. In a total exposure of more than 100 kg$\cdot$yr, taken under record-low background conditions, no signal was found. The corresponding half-life limit is >1.8$\cdot$10$^{26}$ yr at 90% C.L., and coincides with the median sensitivity for the null hypothesis. Under standard assumptions and given the most recent nuclear structure calculations for Ge-76, the effective Majorana neutrino mass is constrained to <[79,180] meV. The Large Enriched Germanium Experiment for Neutrinoless double beta Decay (LEGEND) is about to carry on with this search. The initial 200-kg phase, LEGEND-200, is currently under construction and is going to reach a half-life sensitivity one order of magnitude above the current limits, while LEGEND-1000 will have sensitivity beyond 10$^{28}$ yr and probe the full parameter space spanned by the inverted ordering scenario. I will present major building blocks of the final GERDA result, provide the status of the LEGEND experimental program and discuss the implications for the field.

Primary author

Christoph Wiesinger (Technical University of Munich)

Presentation materials