Could the 21-cm absorption be explained by the dark matter suggested by ${}^8$Be transitions?

Abstract

The stronger than expected 21-cm absorption was observed by EDGES recently, and another anomaly of ${}^8$Be transitions would be signatures of new interactions. These two issues may be related to each other, e.g., pseudoscalar $A$ mediated fermionic millicharged dark matter (DM), and the 21-cm absorption could be induced by photon mediated scattering between MeV millicharged DM and hydrogen. This will be explored in this paper. For fermionic millicharged DM $\bar{\chi }\chi$ with masses in a range of $2m_A<2m_{\chi }<3m_A$, the p-wave annihilation $\bar{\chi }\chi \to AA$ would be dominant during DM freeze-out. The s-wave annihilation $\bar{\chi }\chi$ $\to A,\gamma$ $\to e^{+}{e}^{-}$ is tolerant by constraints from CMB and the 21-cm absorption. The millicharged DM can evade constraints from direct detection experiments. The process of $K^{+}\to {\pi }^{+}{\pi }^0$ with the invisible decay ${\pi }^0\to \bar{\chi }\chi$ could be employed to search for the millicharged DM, and future high intensity $K^{+}$ sources, such as NA62, will do the job.

arXiv comment6 pages, 2 figures, the accepted version, EPJC

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Cited by in corpus (7)

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• Implications of the possible 21-cm line excess at cosmic dawn on dynamics of interacting dark energy
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