First Limits on sub-MeV BSM Physics in the Neutrino Sector from Phase-II of the BeEST Experiment

ORAL

Abstract

The lepton sector of the Standard Model (SM) provides perhaps the best window into Beyond Standard Model (BSM) physics through investigations into non-zero neutrino mass states.  Searches for mass states in the keV-MeV range - associated with mostly sterile flavors - are among the most highly motivated since they have the right cosmological properties to explain the observed dark matter in our universe and may offer insight into the baryon asymmetry of the Universe.  The Beryllium Electron-capture with Superconducting Tunnel junctions (BeEST) experiment probes BSM neutrino physics in the sub-MeV mass range using momentum reconstruction in 7Be electron capture (EC) decay with quantum sensors.  In this talk, I will present our first limits from Phase-II of the experiment which used a single sensor counting for 28 days at low rate [PRL 126, 021803 (2021)] which are up to an order of magnitude better than all previous decay limits in the 100 - 860 keV region.

*This work is supported by the Office of Nuclear Physics in the U.S. Department of Energy's Office of Science under Grant DE-SC0021245, the LLNL Laboratory Directed Research and Development program through Grants No. 19-FS-027 and No. 20-LW-006, and the Natural Sciences and Engineering Research Council of Canada. TRIUMF receives federal funding via a contribution agreement with the National Research Council of Canada. This research was performed under appointment to the Nuclear Nonproliferation International Safeguards Fellowship Program sponsored by the Department of Energy, National Nuclear Security Administrations Office of International Nuclear Safeguards (NA-241). The theoretical work was performed as part of the European Metrology Programme for Innovation and Research (EMPIR) Projects No. 17FUN02 MetroMMC and No. 20FUN09 PrimA-LTD. This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract No. DE-AC52- 07N

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Publication: - Phys. Rev. Lett. 126, 021803 (2021)
- Journ. Low. Temp. Phys. 200, 200 (2020)
- Phys. Rev. Lett. 125, 032701 (2020)

Presenters

  • Kyle G Leach

    • Colorado School of Mines

Authors

  • Kyle G Leach

    • Colorado School of Mines