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arXiv · 2605.30422

Millicharged Particle Constraints from Asymptotic Giant Branch Stars

Damiano F. G. Fiorillo·Giuseppe Lucente·Jeremy Sakstein·Edoardo Vitagliano
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Abstract

We investigate the effect of millicharged particles (MCPs) with electric charge $qe\ll e$ and mass $m_\chi$ on the late-stage evolution phases of low-mass stars in globular clusters. We predict the $R_2$ parameter -- the ratio of the number of stars in the asymptotic giant branch (AGB) phase to the number of stars in the horizontal branch (HB) phase -- and compare it against globular cluster data. While the production of MCPs shortens both the HB and AGB lifetimes, a larger reduction in the AGB phase arises from the higher temperatures in the helium-burning shell. We find the strongest bounds in the range $10\,\mathrm{keV}\lesssim m_\chi\lesssim 100\,\mathrm{keV}$, reaching charges as small as $q\simeq 5\times10^{-13}$ and surpassing existing constraints by up to two orders of magnitude.

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Damiano F. G. Fiorillo, Giuseppe Lucente, Jeremy Sakstein, Edoardo Vitagliano. 2026-05-28. Millicharged Particle Constraints from Asymptotic Giant Branch Stars. https://arxiv.org/abs/2605.30422

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