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The recombination history of the Universe provides a useful tool forconstraining the annihilation of dark matter particles. Even a small fractionof dark matter particles annihilated during the cosmic dark age can providesufficient energy to affect the ionization state of the baryonic gas. Althoughthis effect is too small for neutralinos, lighter dark matter particlecandidates, e.g. with mass of 1-100 MeV, which was proposed recently to explainthe observed excess of positrons in the Galactic Center, may generateobservable differences in the cosmic microwave background (CMB) temperature andpolarization anisotropies. The annihilations at the era of recombinationaffects mainly the CMB anisotropy at small angular scales (large $\ell$), andis distinctively different from the effect of early reionization. We perform amulti-parameter analysis of the CMB data, including the both the WMAP firstyear and three year data, and the ACBAR, Boomerang, CBI, and VSA data. Assumingthat the observed excess of $e^+e^-$ pairs in the galactic center region isproduced by dark matter annihilation, and that a sizable fraction of the energyproduced in the annihilation is deposited in the baryonic gas duringrecombination, we obtain a %95 dark matter mass limit of $M<8 \MeV$ with thecurrent data set.Comment: version matching that appeared on PR

Impacts of dark matter particle annihilation on recombination and the anisotropies of the cosmic microwave background