Published June 17, 2025
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Final Results of the Majorana Demonstrator's Search for Double-Beta Decay of ^{76}Ge to Excited States of ^{76}Se.

Creators

  • 1. Pacific Northwest National Laboratory, Richland, Washington 99354, USA.
  • 2. Pacific Northwest National Laboratory
  • 3. University of South Carolina, Department of Physics and Astronomy, Columbia, South Carolina 29208, USA.
  • 4. University of South Carolina
  • 5. Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830, USA.
  • 6. Oak Ridge National Laboratory
  • 7. National Research Center "Kurchatov Institute, ," Kurchatov Complex of Theoretical and Experimental Physics, Moscow, 117218 Russia.
  • 8. Kurchatov Institute
  • 9. North Carolina State University, Department of Physics, Raleigh, North Carolina 27695, USA.
  • 10. North Carolina State University
  • 11. Triangle Universities Nuclear Laboratory, Durham, North Carolina 27708, USA.
  • 12. University of North Carolina, Department of Physics and Astronomy, Chapel Hill, North Carolina 27514, USA.
  • 13. Duke University, Department of Physics, Durham, North Carolina 27708, USA.
  • 14. Duke University
  • 15. Lawrence Berkeley National Laboratory, Nuclear Science Division, Berkeley, California 94720, USA.
  • 16. Lawrence Berkeley National Laboratory
  • 17. South Dakota Mines, Rapid City, South Dakota 57701, USA.
  • 18. Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
  • 19. Los Alamos National Laboratory
  • 20. Centro de Investigaciones Energéticas, Medioambientales y Tecnológicas CIEMAT, 28040, Madrid, Spain.
  • 21. University of Washington, Center for Experimental Nuclear Physics and Astrophysics, and Department of Physics, Seattle, Washington 98195, USA.
  • 22. University of Washington
  • 23. University of Tennessee, Department of Physics and Astronomy, Knoxville, Tennessee 37916, USA.
  • 24. University of Tennessee
  • 25. Osaka University, Research Center for Nuclear Physics, Ibaraki, Osaka 567-0047, Japan.
  • 26. Osaka University
  • 27. Indiana University, Center for Exploration of Energy and Matter, and Department of Physics, Bloomington, Indiana 47405, USA.
  • 28. Indiana University
  • 29. Williams College, Physics Department, Williamstown, Massachusetts 01267, USA.
  • 30. University of California San Diego, Hal𝚤c𝚤oğlu Data Science Institute, Department of Physics, La Jolla, California 92093, USA.
  • 31. University of California, San Diego
  • 32. University of South Dakota, Department of Physics, Vermillion, South Dakota 57069, USA.
  • 33. Joint Institute for Nuclear Research, Dubna, 141980 Russia.

Description

^{76}Ge can ββ decay into three possible excited states of ^{76}Se, with the emission of two or, if the neutrino is Majorana, zero neutrinos. None of these six transitions have yet been observed. The Majorana Demonstrator was designed to study ββ decay of ^{76}Ge using a low background array of high purity germanium detectors. With 98.2 kg-y of isotopic exposure, the demonstrator sets the strongest half-life limits to date for all six transition modes. For 2νββ to the 0_{1}^{+} state of ^{76}Se, this search has begun to probe for the first time half-life values predicted using modern many-body nuclear theory techniques, setting a limit of T_{1/2}>1.5×10^{24}  y (90% CL).
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