First Results on the Search for Lepton Number Violating Neutrinoless Double-(Formula presented) Decay with the LEGEND-200 Experiment

(LEGEND Collaboration)

doi:10.1103/25tk-nctn

First Results on the Search for Lepton Number Violating Neutrinoless Double-(Formula presented) Decay with the LEGEND-200 Experiment

(LEGEND Collaboration)

University of North Carolina
Triangle Universities Nuclear Laboratory
Max-Planck-Institut für Kernphysik
University College London (UCL)
Simon Fraser University
Physik-Institut der Universität Zürich
University of South Carolina
Oak Ridge National Laboratory
University of Texas at Austin
National Research Centre "Kurchatov Institute"
Laboratori Nazionali del Gran Sasso
Duke University
Sezione INFN di Roma La Sapienza
Sez. di Roma Tre
Institute for Nuclear Research of the Russian Academy of Sciences
Gran Sasso Science Institute
North Carolina State University
University of Washington
Politecnico di Milano
INFN Sezione di Milano
University of Liverpool
University of Padova
Dipartimento di Fisica 'G. Galilei' and INFN
Universit̀ Degli Studi di Milano-Bicocca
Sezione INFN di Milano Bicocca
University of Milan
Lawrence Berkeley National Laboratory
South Dakota Mines
Technical University of Munich
University of South Dakota
University of Tennessee
Los Alamos National Laboratory
University of Tübingen
University of New Mexico
Joint Inst. for Nuclear Research
Indiana University Bloomington
INFN, Laboratori Nazionali Di Frascati
Max-Planck-Institut für Physik
Jagiellonian University
Institute of Experimental and Applied Physics Czech Technical University in Prague
Technische Universität Dresden
European Commission
Lancaster University
Comenius University
Tennessee Technological University
National Research Nuclear University MEPhI
Department of Physics
University of California, San Diego
Universitá di L'Aquila
Queen's University
University of Warwick
Inst. Polymerforschung Dresden e.V.
Leibniz-Institut für Kristallzüchtung

Research output: Contribution to journal › Article › peer-review

16 Scopus citations

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	https://doi.org/10.1103/25tk-nctn
State	Published - 16 Jan 2026

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10.1103/25tk-nctn

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@article{464cd2d8d8394ad38631554e9da8ff37,

title = "First Results on the Search for Lepton Number Violating Neutrinoless Double-(Formula presented) Decay with the LEGEND-200 Experiment",

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.",

author = "\{(LEGEND Collaboration)\} and H. Acharya and N. Ackermann and M. Agostini and A. Alexander and C. Andreoiu and Araujo, \{G. R.\} and Avignone, \{F. T.\} and M. Babicz and W. Bae and Bakalyarov, \{A. M.\} and M. Balata and Barabash, \{A. S.\} and Barbeau, \{P. S.\} and Barton, \{C. J.\} and L. Baudis and C. Bauer and E. Bernieri and L. Bezrukov and Bhimani, \{K. H.\} and V. Biancacci and E. Blalock and Borden, \{S. J.\} and G. Borghi and F. Borra and B. Bos and A. Boston and V. Bothe and R. Bouabid and R. Brugnera and N. Burlac and M. Busch and S. Calgaro and L. Canonica and S. Capra and M. Carminati and Carney, \{R. M.D.\} and C. Cattadori and R. Cesarano and Chan, \{Y. D.\} and Chapman, \{J. R.\} and A. Chernogorov and Chiu, \{P. J.\} and Christofferson, \{C. D.\} and Clark, \{M. L.\} and Colon-Rivera, \{A. I.\} and T. Comellato and V. D{\textquoteright}Andrea and R. Deckert and S. Mertens and S. Sch{\"o}nert",

note = "Publisher Copyright: Published by the American Physical Society.",

year = "2026",

month = jan,

day = "16",

doi = "10.1103/25tk-nctn",

language = "English",

volume = "136",

journal = "Physical Review Letters",

issn = "0031-9007",

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T1 - First Results on the Search for Lepton Number Violating Neutrinoless Double-(Formula presented) Decay with the LEGEND-200 Experiment

AU - (LEGEND Collaboration)

AU - Acharya, H.

AU - Ackermann, N.

AU - Agostini, M.

AU - Alexander, A.

AU - Andreoiu, C.

AU - Araujo, G. R.

AU - Avignone, F. T.

AU - Babicz, M.

AU - Bae, W.

AU - Bakalyarov, A. M.

AU - Balata, M.

AU - Barabash, A. S.

AU - Barbeau, P. S.

AU - Barton, C. J.

AU - Baudis, L.

AU - Bauer, C.

AU - Bernieri, E.

AU - Bezrukov, L.

AU - Bhimani, K. H.

AU - Biancacci, V.

AU - Blalock, E.

AU - Borden, S. J.

AU - Borghi, G.

AU - Borra, F.

AU - Bos, B.

AU - Boston, A.

AU - Bothe, V.

AU - Bouabid, R.

AU - Brugnera, R.

AU - Burlac, N.

AU - Busch, M.

AU - Calgaro, S.

AU - Canonica, L.

AU - Capra, S.

AU - Carminati, M.

AU - Carney, R. M.D.

AU - Cattadori, C.

AU - Cesarano, R.

AU - Chan, Y. D.

AU - Chapman, J. R.

AU - Chernogorov, A.

AU - Chiu, P. J.

AU - Christofferson, C. D.

AU - Clark, M. L.

AU - Colon-Rivera, A. I.

AU - Comellato, T.

AU - D’Andrea, V.

AU - Deckert, R.

AU - Mertens, S.

AU - Schönert, S.

N1 - Publisher Copyright: Published by the American Physical Society.

PY - 2026/1/16

Y1 - 2026/1/16

N2 - 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.

AB - 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.

UR - https://www.scopus.com/pages/publications/105027730571

U2 - 10.1103/25tk-nctn

DO - 10.1103/25tk-nctn

M3 - Article

AN - SCOPUS:105027730571

SN - 0031-9007

VL - 136

JO - Physical Review Letters

JF - Physical Review Letters

IS - 2

M1 - 022701

ER -

First Results on the Search for Lepton Number Violating Neutrinoless Double-(Formula presented) Decay with the LEGEND-200 Experiment

Abstract

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