Luigi Pertoldi (TUM): The LEGEND project: probing Majorana neutrinos beyond the inverted ordering
Based on the success of GERDA and MAJORANA collaborations, the next-generation LEGEND experimental program aims at searching for lepton-number-violating neutrinoless double-beta decays in 76Ge with unprecedented sensitivity, and to cover the full parameter space of the Majorana effective mass allowed by the inverted ordering. The detection principle is to operate high-purity germanium detectors enriched in 76Ge in a ultra-low-background liquid argon bath, instrumented as an active detector to detect the scintillation light produced by backgrounds from trace radioactive contaminants. The first phase LEGEND-200, aiming to reach a sensitivity of 1027 years on the beta half-life by deploying 200 kg of enriched material in the GERDA cryostat, is currently being commissioned at the Laboratori Nazionali del Gran Sasso. The collaboration is committed to build a ton-scale experiment capable to reach sensitivities beyond 1028 years. LEGEND-1000, already at his pre-conceptual design stage, has been recently recognized as one of the most promising ton-scale double-beta projects to be funded by the US Department of Energy.
Marco Drewes (Université catolique de Louvain): Physics Goals of LEGEND - A Theoretical Perspective
The question whether neutrinos are their own antiparticles or not has important implications for several branches of particle physics and cosmology. A positive answer would prove that lepton number is violated in Nature, implying the breaking of one of the global symmetries of the Standard Model. This would provide an important hint towards understanding the mechanism that generates the light neutrino masses, and possible embeddings of the Standard Model into a more fundamental theory of Nature. In addition, lepton number violation may be a key ingredient for the generation of the matter-antimatter asymmetry in the primordial plasma that is thought to be the origin of baryonic matter in the observable universe. LEGEND provides one of the most sensitive experimental probes of lepton number violation in foreseeable time. In this talk we will discuss the implications of a potential discovery for neutrino mass model building and cosmology. We will also comment on the complementarity with accelerator based experiments. In models with a comparably low New Physics scale LEGEND can, together with data from the LHC, help to pin down the mechanism of neutrino mass generation and the origin of matter in the observable universe.