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T: Fachverband Teilchenphysik

T 29: Invited Topical Talks 2

T 29.3: Eingeladener Vortrag

Dienstag, 22. März 2022, 14:50–15:15, T-H16

From GERDA to LEGEND - Hunting no neutrinos — •Christoph Wiesinger — Max-Planck-Institut für Physik, München — Physik-Department, Technische Universität München, Garching

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 that are their own anti-particles. Double beta decay offers a unique probe for this hypothesis. Finding no neutrinos, but 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 this mono-energetic peak. The Germanium Detector Array (GERDA) experiment has operated 40 kg of enriched germanium in an instrumented low-background liquid argon environment. In a total exposure of more than 100 kg yr, taken under record-low background conditions, no signal was found. The corresponding half-life limit for neutrinoless double beta decay of ⁷⁶Ge is >1.8·10²⁶ yr at 90% C.L., and coincides with the median sensitivity for the null hypothesis. The Large Enriched Germanium Experiment for Neutrinoless double beta Decay (LEGEND) is about to expand this search towards 10²⁸ yr and beyond. Following LEGEND-200, the initial 200-kg phase currently under construction, LEGEND-1000 will probe the full parameter space spanned by the inverted ordering scenario.