Abstract
We consider dark matter which has nonzero electromagnetic form factors like electric/magnetic dipole moments and anapole moment for fermionic dark matter and Rayleigh form factor for scalar dark matter. We consider dark matter mass ${m}_{\ensuremath{\chi}}>\mathcal{O}(\mathrm{MeV})$ and put constraints on their mass and electromagnetic couplings from cosmic microwave background (CMB) and large scale structure (LSS) observations. Fermionic dark matter with nonzero electromagnetic form factors can annihilate to ${e}^{+}{e}^{\ensuremath{-}}$ and scalar dark matter can annihilate to $2\ensuremath{\gamma}$ at the time of recombination and distort the CMB. We analyze dark matter with multipole moments with Planck and baryon acoustic oscillations (BAO) observations. We find upper bounds on anapole moment ${g}_{A}<7.163\ifmmode\times\else\texttimes\fi{}{10}^{3}\text{ }\text{ }{\mathrm{GeV}}^{\ensuremath{-}2}$, electric dipole moment $\mathcal{D}<7.978\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}9}\text{ }\text{ }e\text{ }\mathrm{cm}$, magnetic dipole moment $\ensuremath{\mu}<2.959\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}7}{\ensuremath{\mu}}_{B}$, and the bound on Rayleigh form factor of dark matter is ${g}_{4}/{\mathrm{\ensuremath{\Lambda}}}_{4}^{2}<1.085\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}2}\text{ }\text{ }{\mathrm{GeV}}^{\ensuremath{-}2}$ with 95% C.L.
Highlights
It is well accepted that formation of large scale structures and the rotation curves of galaxies require an extra dark matter (DM) component beyond the known particles of the standard model
Fermionic dark matter with nonzero electromagnetic form factors can annihilate to eþe− and scalar dark matter can annihilate to 2γ at the time of recombination and distort the cosmic microwave background (CMB)
We find upper bounds on anapole moment gA < 7.163 × 103 GeV−2, electric dipole moment D < 7.978 × 10−9 e cm, magnetic dipole moment μ < 2.959 × 10−7μB, and the bound on Rayleigh form factor of dark matter is g4=Λ24 < 1.085 × 10−2 GeV−2 with 95% C.L
Summary
It is well accepted that formation of large scale structures and the rotation curves of galaxies require an extra dark matter (DM) component beyond the known particles of the standard model. Direct detection experiments, which rely on nuclear scattering, have ruled out a large parameter space These techniques are not efficient in measuring dark matter of sub-GeV mass [1,2]. The low-l correlations between polarization fluctuations are enhanced due to increased freeze-out value of the ionization fraction of the universe after recombination These effects on CMB are significant and can be used to put constraints on thermal averaged annihilation cross section hσvi. For fermionic dark matter the χχ → γγ annihilation cross section is quartic in dipole moments and the bounds from this process are much weaker [29] than the ones we derive in this paper from CMB.
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