Narrowing the window for millicharged particles by CMB anisotropy

S. L. Dubovsky, D. S. Gorbunov, G. I. Rubtsov

    Research output: Contribution to journalArticlepeer-review

    Abstract

    We calculate the cosmic microwave background (CMB) anisotropy spectrum in models with millicharged particles of electric charge q ∼ 10(-6)-10(-1) in units of electron charge. We find that a large region of the parameter space for the millicharged particles exists where their effect on the CMB spectrum is similar to the effect of baryons. Using WMAP data on the CMB anisotropy and assuming the Big Bang nucleosynthesis value for the baryon abundance, we find that only a small fraction of cold dark matter, OHmcph 20 < 0.007 (at 95% CL), may consist of millicharged particles with the parameters (charge and mass) from this region. This bound significantly narrows the allowed range of the parameters of millicharged particles. In models without paraphotons, millicharged particles are now excluded as a dark matter candidate. We also speculate that recent observation of 511-keV γ rays from the Galactic bulge may be an indication that a (small) fraction of cold dark matter is comprised of millicharged particles.

    Original languageEnglish (US)
    Pages (from-to)1-5
    Number of pages5
    JournalJETP Letters
    Volume79
    Issue number1
    DOIs
    StatePublished - 2004

    ASJC Scopus subject areas

    • Physics and Astronomy (miscellaneous)

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