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MeV-mass dark matter and primordial nucleosynthesis

Pasquale D. Serpico·Georg G. Raffelt
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Abstract

The annihilation of new dark matter candidates with masses $m_X$ in the MeV range may account for the galactic positrons that are required to explain the 511 keV $γ$-ray flux from the galactic bulge. We study the impact of MeV-mass thermal relic particles on the primordial synthesis of $^2$H, $^4$He, and $^7$Li. If the new particles are in thermal equilibrium with neutrinos during the nucleosynthesis epoch they increase the helium mass fraction for $m_X\alt 10$ MeV and are thus disfavored. If they couple primarily to the electromagnetic plasma they can have the opposite effect of lowering both helium and deuterium. For $m_X=4$--10 MeV they can even improve the overall agreement between the predicted and observed $^2$H and $^4$He abundances.

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Pasquale D. Serpico, Georg G. Raffelt. 2004-05-27. MeV-mass dark matter and primordial nucleosynthesis. https://doi.org/10.1103/physrevd.70.043526

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