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arXiv · 2507.17955

Constraints on millicharged particles from nuclear gamma-decays

Ting Gao·Maxim Pospelov
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Abstract

We consider nuclear gamma decays and $\gamma$-emitting reactions that can be an efficient source of hypothetical millicharged particles ($\chi$). In particular, we revisit the production of millicharged particles in nuclear reactor environment, pointing out that $\gamma$ cascades from $^{239}$U is an overlooked yet a powerful source of $\chi\bar\chi$ pairs. This leads to an increased flux compared to previous studies. We then apply new estimates of the flux to derive novel limits on the value of millicharge, $\varepsilon = Q_\chi/e$, from the electron recoil searched for in a variety of experiments placed in proximity to the reactor cores. The derived limits on $\varepsilon$ are the strongest in the interval of masses $\sim 0.7-2$ MeV. We also derive the MCP flux from the Sun and point out potential sensitivity of the low-threshold dark matter search experiments.

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Ting Gao, Maxim Pospelov. 2025-07-23. Constraints on millicharged particles from nuclear gamma-decays. https://doi.org/10.1103/ys3l-3bcd

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