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arXiv · 2606.15014

Ultralow-Energy Measurements using the Startpoint of $\beta$ Decays

Daniel Kodroff·Michael R. Williams
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Abstract

We propose a novel measurement of $\beta$ decays using low-temperature solid-state detector technologies. The $\beta$ startpoint, where the $\beta$ kinetic energy is zero, offers a unique probe of weak nuclear physics that has not yet been exploited experimentally. We describe how this technique enables searches for heavy sterile neutrinos in the keV--MeV energy range and show that, with current technologies, sensitivities to sterile neutrino coupling to electrons can be achieved that exceed the current best constraints. The spectrum produced by the recoiling daughter ion also offers a calibration of the nuclear recoil response, addressing key assumptions in sub-GeV dark matter searches. We outline a potential experimental scheme using neutron activation to produce $^{32}$P $\textit{in situ}$ in a silicon substrate, discuss projected sensitivities to sterile neutrinos, and evaluate the prospects for nuclear recoil calibrations.

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Daniel Kodroff, Michael R. Williams. 2026-06-12. Ultralow-Energy Measurements using the Startpoint of $\beta$ Decays. https://arxiv.org/abs/2606.15014

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