http://arxiv.org/abs/1910.04779
While the behavior of the dominant component of the dark matter is reasonably well established by cosmological observables, its particle nature and interactions with the rest of the matter are not known. We consider three dark matter models that admit electromagnetic interaction between baryons and dark matter: (a) milli-charged particle (CCDM) of charge $q_{\rm ccdm}$ and mass $m_{\rm ccdm}$, (b) a neutral atom of two charged particles of mass $m_{\rm dd}$ (DD), and (c) a neutral atom of doubly charged particle and helium nucleus (HeD). We derive and discuss in detail the formation, stability, and interaction of these atoms with baryons. These new interactions are incorporated into the publicly-available code CLASS to obtain the matter power spectra and CMB anisotropies. We carry out MCMC analysis to constrain the fraction of interacting dark matter allowed by Planck data. For the range of allowed parameters, all the cold dark matter could be the form of HeD atoms or DD atoms if $m_{\rm dd} \gtrsim 25 \, \rm GeV$. The MCMC analysis suggests that the current data prefers, at 1$\sigma$ level, a fraction of nearly 5% of either CCDM or DD dark matter for the following parameters: $q_{\rm ccdm} = 10^{-6}e$, $m_{\rm ccdm} = 50 \, \rm MeV$ or $m_{\rm dd} = 10 \, \rm GeV$.
G. P and S. Sethi
Mon, 14 Oct 19
48/69
Comments: 24 pages, 5 figures
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