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Article Dans Une Revue Physical Review C Année : 2020

Improved calculations of beta decay backgrounds to new physics in liquid xenon detectors

Résumé

We present high-precision theoretical predictions for the electron energy spectra for the ground-state to ground-state $\beta$ decays of $^{214}$Pb, $^{212}$Pb, and $^{85}$Kr most relevant to the background of liquid xenon dark matter detectors. The effects of nuclear structure on the spectral shapes are taken into account using large-scale shell model calculations. Final spectra also include atomic screening and exchange effects. The impact of nuclear structure effects on the $^{214}$Pb and $^{212}$Pb spectra below $\approx100$ keV, pertinent for several searches for new physics, are found to be comparatively larger than those from the atomic effects alone. We find that the full calculation for $^{214}$Pb ($^{212}$Pb) predicts 15.0-23.2% (12.1-19.0%) less event rate in a 1-15 keV energy region of interest compared to the spectrum calculated as an allowed transition when using values of the weak axial vector coupling in the range $g_{\rm A}=0.7-1.0$. The discrepancy highlights the importance of both a proper theoretical treatment and the need for direct measurements of these spectra for a thorough understanding of $\beta$ decay backgrounds in future experiments.
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Dates et versions

hal-03085500 , version 1 (21-12-2020)

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S.J. Haselschwardt, J. Kostensalo, Xavier Mougeot, J. Suhonen. Improved calculations of beta decay backgrounds to new physics in liquid xenon detectors. Physical Review C, 2020, 102, pp.065501. ⟨10.1103/PhysRevC.102.065501⟩. ⟨hal-03085500⟩
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