Cosmological implications of electromagnetically interacting dark matter: milli-charged particles and atoms with singly and doubly charged dark matter. (arXiv:1910.04779v1 [astro-ph.CO])
<a href="http://arxiv.org/find/astro-ph/1/au:+P_G/0/1/0/all/0/1">Gautham A P</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sethi_S/0/1/0/all/0/1">Shiv Sethi</a>
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 $m_{rm dd} = 10 , rm GeV$.
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 $m_{rm dd} = 10 , rm GeV$.
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