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Monte Carlo Modeling of eV-Scale Backgrounds in Superconducting Tunnel Junctions from Gamma-Ray Interactions

ORAL

Abstract

The BeEST experiment searches for physics beyond the standard model (BSM) in the neutrino sector by utilizing the electron capture (EC) decay of 7Be. The 7Be is embedded in superconducting tunnel junction (STJ) sensors such that the low-energy (eV-scale) radiation is detected with high efficiency. In 10% of the decays, a 478 keV gamma-ray is emitted in the dexcitation of the 7Li daughter nucleus. While the gamma ray does not interact in the STJ (~0.5um), it scatters in the silicon substrate that the STJ is deposited on. This then results in a low-energy background seen on the energy spectra read from the quantum sensor. In this talk I will discuss our modeling of this background using a python based Monte Carlo of light-matter interactions and subsequent phonon propagation.

* The BeEST experiment is funded in part by the Gordon and Betty Moore Foundation (10.37807/GBMF11571), the DOE-SC Office of Nuclear Physics under Award Numbers DE-SC0021245 and DE-FG02-93ER40789, and the LLNL Laboratory Directed Research and Development program through Grants No. 19-FS-027 and No. 20-LW-006. TRIUMF receives federal funding via a contribution agreement with the National Research Council of Canada. 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- 07NA27344.

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Presenters

  • Caitlyn J Stone-Whitehead

    Colorado School of Mines

Authors

  • Caitlyn J Stone-Whitehead

    Colorado School of Mines