Dark matter from CP symmetry of order 4: evolution in the asymmetric regime. (arXiv:1812.05525v1 [hep-ph])
<a href="http://arxiv.org/find/hep-ph/1/au:+Ivanov_I/0/1/0/all/0/1">Igor P. Ivanov</a>, <a href="http://arxiv.org/find/hep-ph/1/au:+Laletin_M/0/1/0/all/0/1">Maxim Laletin</a>
Multi-Higgs models equipped with global symmetries produce scalar dark matter
(DM) candidates stabilized by the unbroken symmetry. It is remarkable that a
conserved CP symmetry can also stabilize DM candidates, provided it is a CP
symmetry of order higher than two. CP4 3HDM, the three-Higgs-doublet model with
CP symmetry of order 4, is the simplest example of this kind. It contains two
mass-degenerate scalar DM candidates $varphi$ and $barvarphi$, each of them
being a CP4 eigenstate and, therefore, its own antiparticle. A novel
phenomenological feature of this model is the presence of $varphivarphi
leftrightarrow barvarphibarvarphi$ conversion process, which conserves CP.
It offers a rare example of DM models in which self-interaction in the dark
sector can significantly affect cosmological and astrophysical observables.
Here, we explore the thermal evolution of these DM species in the asymmetric
regime. We assume that a mechanism external to CP4 3HDM produces an initial
imbalance of the densities of $varphi$ and $barvarphi$. As the Universe
cools down, we track the evolution of the asymmetry through different stages,
and determine how the final asymmetry depends on the interplay between the
conversion and annihilation $varphibarvarphi to $ SM and on the initial
conditions. We begin with the analytic treatment of Boltzmann equations,
present a detailed qualitative description of the process, and then corroborate
it with numerical results obtained using a dedicated computer code. Finally, we
check if the model can produce an observable indirect detection signal.
Multi-Higgs models equipped with global symmetries produce scalar dark matter
(DM) candidates stabilized by the unbroken symmetry. It is remarkable that a
conserved CP symmetry can also stabilize DM candidates, provided it is a CP
symmetry of order higher than two. CP4 3HDM, the three-Higgs-doublet model with
CP symmetry of order 4, is the simplest example of this kind. It contains two
mass-degenerate scalar DM candidates $varphi$ and $barvarphi$, each of them
being a CP4 eigenstate and, therefore, its own antiparticle. A novel
phenomenological feature of this model is the presence of $varphivarphi
leftrightarrow barvarphibarvarphi$ conversion process, which conserves CP.
It offers a rare example of DM models in which self-interaction in the dark
sector can significantly affect cosmological and astrophysical observables.
Here, we explore the thermal evolution of these DM species in the asymmetric
regime. We assume that a mechanism external to CP4 3HDM produces an initial
imbalance of the densities of $varphi$ and $barvarphi$. As the Universe
cools down, we track the evolution of the asymmetry through different stages,
and determine how the final asymmetry depends on the interplay between the
conversion and annihilation $varphibarvarphi to $ SM and on the initial
conditions. We begin with the analytic treatment of Boltzmann equations,
present a detailed qualitative description of the process, and then corroborate
it with numerical results obtained using a dedicated computer code. Finally, we
check if the model can produce an observable indirect detection signal.
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