3 research outputs found
MeV-mass dark matter and primordial nucleosynthesis
The annihilation of new dark matter candidates with masses in the MeV
range may account for the galactic positrons that are required to explain the
511 keV -ray flux from the galactic bulge. We study the impact of
MeV-mass thermal relic particles on the primordial synthesis of H, He,
and 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 --10 MeV they can even improve the overall
agreement between the predicted and observed H and He abundances.Comment: 11 pages, 10 figures, references and two appendices added,
conclusions unchanged; accepted for publication in Phys.Rev.