Abstract
The LEGEND Collaboration is searching for neutrinoless double-beta ((Formula presented)) decay by operating high-purity germanium detectors enriched in (Formula presented) in a low-background liquid argon environment. Building on key technological innovations from the GERmanium Detector Array (GERDA) experiment and the MAJORANA DEMONSTRATOR experiment, LEGEND-200 has performed a first (Formula presented) decay search based on 61.0 kg yr of data. Over half of this exposure comes from our highest performing detectors, including newly developed inverted-coaxial detectors, and is characterized by an estimated background level of (Formula presented) in the (Formula presented) decay signal region. A combined analysis of data from GERDA, the MAJORANA DEMONSTRATOR, and LEGEND-200, characterized by a 90% confidence level exclusion sensitivity of (Formula presented) on the half-life of (Formula presented) decay, reveals no evidence for a signal and sets a new observed lower limit at (Formula presented) (90% confidence level). Assuming the decay is mediated by Majorana neutrinos, this corresponds to an upper limit on the effective Majorana mass in the range (Formula presented), depending on the adopted nuclear matrix element.
| Original language | English |
|---|---|
| Article number | 022701 |
| Journal | Physical Review Letters |
| Volume | 136 |
| Issue number | 2 |
| DOIs | |
| State | Published - Jan 16 2026 |
Funding
The authors acknowledge support from the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under Federal Prime Agreements No. DE-AC02-05CH11231, No. DE-AC05-00OR22725, and No. LANLEM78, and under Awards No. DE-SC0017594, No. DE-FG02-97ER41020, No. DE-FG02-97ER41033, No. DE-FG02-97ER41041, No. DE-FG02-97ER41042, No. DE-SC0017594, No. DOE DE-SC0022339, No. DE-SC0012612, No. DE-SC0018060, and No. DE-SC0014445. We acknowledge support from the Nuclear Precision Measurements program of the Division of Physics of the National Science Foundation through Grants No. NSF PHY-1812374, No. NSF PHY-1812356, No. NSF-PHY-2111140, No. NSF PHY-1812409, No. NSF PHY-2209530, and No. NSF PHY-2312278, and from the Office of International Science and Engineering of the National Science Foundation through Grant No. NSF OISE 1743790. We gratefully acknowledge the support of the U.S. Department of Energy through the LANL, ORNL, and LBNL Laboratory Directed Research and Development (LDRD) Programs. This research is funded in part by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)—Excellence Cluster ORIGINS EXC No. 2094-39078331; No. SFB1258-283604770. We acknowledge the support of the German Federal Ministry for Education and Research (BMBF) through Grant No. 05A2023 and the Max Planck Society (MPG). This work is supported in part by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (Grant Agreement No. 786430—GemX). We gratefully acknowledge the financial support of the Italian Istituto Nazionale di Fisica (INFN), the Polish National Science Centre (NCN, Grant No. UMO-2020/37/B/ST2/03905), the Polish Ministry of Science and Higher Education (MNiSW, Grants No. DIR/WK/2018/08 and No. 2022/WK/10), the Czech Republic Ministry of Education, Youth and Sports No. LM2023063, the Slovak Research and Development Agency, Grant No. APVV-21-0377, and the Swiss |National Science Foundation (SNF), No. SNF FLARE 20FL20_216572, No. FLARE 20FL20_232670, and No. SNF 200020_219290. This project has received funding and support from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie Grant Agreement No. 860881-HIDDeN. This work has been supported by the Science and Technology Facilities Council (STFC), part of U.K. Research and Innovation (Grants No. ST/W00058X/1 and No. ST/T004169/1). We acknowledge the support of the Natural Sciences and Engineering Research Council of Canada, funding reference No. SAPIN-2017-00023. This research used resources provided by National Energy Research Scientific Computing Center (NERSC), a U.S. Department of Energy Office of Science User Facility at LBNL, and the Oak Ridge Leadership Computing Facility at Oak Ridge National Laboratory. We thank the directors and the staff of the Laboratori Nazionali del Gran Sasso and our colleagues at the Sanford Underground Research Facility for their continuous strong support of the LEGEND experiment. We would like to thank the authors of for providing the posterior distribution of the NME for the decay of considered in this work. The authors acknowledge support from the U.S. Department of Energy, Office of Science, Office of Nuclear Physics under Federal Prime Agreements No. DE-AC02-05CH11231, No. DE-AC05-00OR22725, and No. LANLEM78, and under Awards No. DE-SC0017594, No. DE-FG02-97ER41020, No. DE-FG02-97ER41033, No. DE-FG02-97ER41041, No. DE-FG02-97ER41042, No. DE-SC0017594, No. DOE DE-SC0022339, No. DE-SC0012612, No. DE-SC0018060, and No. DE-SC0014445. We acknowledge support from the Nuclear Precision Measurements program of the Division of Physics of the National Science Foundation through Grants No. NSF PHY-1812374, No. NSF PHY-1812356, No. NSF-PHY-2111140, No. NSF PHY-1812409, No. NSF PHY-2209530, and No. NSF PHY-2312278, and from the Office of International Science and Engineering of the National Science Foundation through Grant No. NSF OISE 1743790. We gratefully acknowledge the support of the U.S. Department of Energy through the LANL, ORNL, and LBNL Laboratory Directed Research and Development (LDRD) Programs. This research is funded in part by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)—Excellence Cluster ORIGINS EXC No. 2094-39078331; No. SFB1258-283604770. We acknowledge the support of the German Federal Ministry for Education and Research (BMBF) through Grant No. 05A2023 and the Max Planck Society (MPG). This work is supported in part by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (Grant Agreement No. 786430—GemX). We gratefully acknowledge the financial support of the Italian Istituto Nazionale di Fisica (INFN), the Polish National Science Centre (NCN, Grant No. UMO-2020/37/B/ST2/03905), the Polish Ministry of Science and Higher Education (MNiSW, Grants No. DIR/WK/2018/08 and No. 2022/WK/10), the Czech Republic Ministry of Education, Youth and Sports No. LM2023063, the Slovak Research and Development Agency, Grant No. APVV-21-0377, and the Swiss |National Science Foundation (SNF), No. SNF FLARE 20FL20_216572, No. FLARE 20FL20_232670, and No. SNF 200020_219290. This project has received funding and support from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie Grant Agreement No. 860881-HIDDeN. This work has been supported by the Science and Technology Facilities Council (STFC), part of U.K. Research and Innovation (Grants No. ST/W00058X/1 and No. ST/T004169/1). We acknowledge the support of the Natural Sciences and Engineering Research Council of Canada, funding reference No. SAPIN-2017-00023. This research used resources provided by National Energy Research Scientific Computing Center (NERSC), a U.S. Department of Energy Office of Science User Facility at LBNL, and the Oak Ridge Leadership Computing Facility at Oak Ridge National Laboratory. We thank the directors and the staff of the Laboratori Nazionali del Gran Sasso and our colleagues at the Sanford Underground Research Facility for their continuous strong support of the LEGEND experiment. We would like to thank the authors of [77] for providing the posterior distribution of the NME for the 0 ν β β decay of Ge 76 considered in this work.