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

Le Zhang, Xuelei Chen, Yi-An Lei, and Zong-guo Si
Phys. Rev. D 74, 103519 – Published 29 November 2006

Abstract

The recombination history of the Universe provides a useful tool for constraining the annihilation of dark matter particles. Even a small fraction of dark matter particles annihilated during the cosmic dark age can provide sufficient energy to affect the ionization state of the baryonic gas. Although this effect is too small for neutralinos, lighter dark matter particle candidates, e.g. with mass of 1–100 MeV, which was proposed recently to explain the observed excess of positrons in the galactic center, may generate observable differences in the cosmic microwave background (CMB) temperature and polarization anisotropies. The annihilations at the era of recombination affects mainly the CMB anisotropy at small angular scales (large ), and is distinctively different from the effect of early reionization. We perform a multiparameter analysis of the CMB data, including both the Wilkinson Microwave Anisotropy Probe (WMAP) first year and three year data, and the ACBAR, Boomerang, CBI, and VSA data. Assuming that the observed excess of e+e pairs in the galactic center region is produced by dark matter annihilation, and that a sizable fraction of the energy produced in the annihilation is deposited in the baryonic gas during recombination, we obtain a 95% dark matter mass limit of M<8MeV with the current data set.

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  • Received 16 March 2006

DOI:https://doi.org/10.1103/PhysRevD.74.103519

©2006 American Physical Society

Authors & Affiliations

Le Zhang1,2, Xuelei Chen1,*, Yi-An Lei3, and Zong-guo Si2

  • 1National Astronomical Observatories, Chinese Academy of Sciences, Beijing, 100012, China
  • 2Department of Physics, Shandong University, Jinan, 250100, China
  • 3Department of Physics, Peking University, Beijing, 100871, China

  • *Electronic address: xuelei@bao.ac.cn

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Vol. 74, Iss. 10 — 15 November 2006

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