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A<sc>bstract</sc> The Electron-Ion Collider (EIC), a forthcoming powerful high-luminosity facility, represents an exciting opportunity to explore new physics. In this article, we study the potential of the EIC to probe the coupling between axion-like particles (ALPs) and photons in coherent scattering. The ALPs can be produced via photon fusion and decay back to two photons inside the EIC detector. In a prompt-decay search, we find that the EIC can set the most stringent bound forma≲ 20 GeV and probe the effective scales Λ ≲ 105GeV. In a displaced-vertex search, which requires adopting an EM calorimeter technology that provides directionality, the EIC could probe ALPs withma≲ 1 GeV at effective scales Λ ≲ 107GeV. Combining the two search strategies, the EIC can probe a significant portion of unexplored parameter space in the 0.2 <ma< 20 GeV mass range.
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This content will become publicly available on April 1, 2026
Blue loops, Cepheids, and forays into axions
Abstract The blue loop stage of intermediate mass stars has been called a “magnifying glass”, where even seemingly small effects in prior stages of evolution, as well as assumptions about stellar composition, rotation, and convection, produce discernible changes. As such, blue loops, and especially the existence and properties of Cepheids, can serve as a laboratory where feebly connected Beyond Standard Model particles such as axions can be gainfully studied. We undertake a careful study of the effects of these putative particles on the blue loop, paying close attention to the evolution of the core potential and the hydrogen profile. Our simulations, performed withMESA, place bounds on the axion-photon coupling using the galactic Cepheid S Mus, with dynamically-determined mass of 6M⊙, as a benchmark. The effects of varying convective overshoot on the core potential and hydrogen profile, and the ensuing changes in the axion constraints, are carefully studied. Along the way, we explore the “mirror principle” induced by the hydrogen burning shell and contrast our results with those existing in the literature. Less conservative (but more stringent) bounds on the axion-photon coupling are given for a 9M⊙model, which is the heaviest that can be simulated if overshoot is incorporated, and tentative projections are given for a 12M⊙model, which is approximately the heaviest tail of the mass distribution of galactic Cepheids determined by pulsation models using Gaia DR2. Our main message is that the reliable simulation and observation (ideally, through dynamical mass determination) of massive Cepheids constitutes an important frontier in axion searches, challenges in modeling uncertainties in the microphysics of the blue loop stage notwithstanding.
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- PAR ID:
- 10588193
- Publisher / Repository:
- IOP Science
- Date Published:
- Journal Name:
- Journal of Cosmology and Astroparticle Physics
- Volume:
- 2025
- Issue:
- 04
- ISSN:
- 1475-7516
- Page Range / eLocation ID:
- 083
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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