Six-Higgs-doublet model for dark matter

We consider an extension of the Higgs sector in the standard model with six Higgs doublets. The gauge couplings are unified without supersymmetry in this model. The lightest of the extra Higgs particles, being stabilized by a discrete symmetry imposed from the outset, presents a plausible candidate for dark matter. For a specific acceptable benchmark point, we show that the model is viable regarding the constraints of relic density, direct detection, and invisible Higgs decay. We comment on the mean free path of the dark matter candidate.

Figure 1

Unification of gauge couplings in SM with $n_H=6$ Higgs doublets at 1-loop (left) and 2-loop (right) runnings.

Figure 2

Relic density versus $M_{\psi }$ for five fixed values of $\lambda$. “Acceptable” Planck limits are also shown.

Figure 3

Relic density versus $\lambda$ for five fixed values of $M_{\psi }$. “Acceptable” Planck limits are also shown.

Figure 4

Direct detection: Nucleon-$\psi$ scattering amplitude versus $M_{\psi }$ for three fixed values of $\lambda$. LUX and Xenon100 limits, above which lie excluded regions, are also shown.

Figure 5

Direct detection: Nucleon-$\psi$ scattering amplitude versus $\lambda$ for five fixed values of $M_{\psi }$. LUX and Xenon100 limits, above which lie excluded regions, are also shown.

Figure 6

Branching ratio of invisible Higgs decay versus $M_{\psi }$ for five fixed values of $\lambda$. The LHC limit, above which is an excluded region, is also shown.

Figure 7

Branching ratio of invisible Higgs decay versus $\lambda$ for five fixed values of $M_{\psi }$. The LHC limit, above which is an excluded region, is also shown.

Figure 8

6HDM at the “symmetric” choice for benchmark point.

Figure 9

Relic density constraint using micrOMEGAs.