Speakers
Description
We present a simple twist in the well studied two Higgs doublet model in the form of an extra interchange symmetry between the two Higgs doublets ($\Phi_1$ $\leftrightarrow$ $\Phi_2$). There is a residual $Z_2$ symmetry that remains unbroken after the original symmetry $\Phi_1$ $\leftrightarrow$ $\Phi_2$ is spontaneously broken. This unbroken $Z_2$ symmetry makes the charged scalars $H^\pm$, the neutral scalar $H$ and the pseudoscalar $A$ to have $Z_2$ negative charges and all the other fields remain $Z_2$ positive. This, in turn, makes the lightest $Z_2$ negative particle, the neutral scalar $H$ to be the candidate for Dark Matter. This neutral scalar $H$ can be much lighter in mass in comparison to the Standard Model-(SM) like neutral scalar $h$ having mass $m_h \simeq 125$ GeV as seen by the LHC. Interestingly this lighter neutral scalar $H$, as well as the charged scalars $H^\pm$ and the pseudoscalar $A$, do not couple to fermions. The lighter neutral scalars also don't have the usual three-point couplings with the Gauge bosons($W^\pm$ and $Z$) present in the Standard Model, but only have four-point couplings with $W^\pm$ and $Z$. As the neutral scalars $h$ and $H$ have interactions among them, the only way to produce the lightest $Z_2$ negative DM candidate $H$ will be through the decays of the SM-like neutral scalar $h$ where this SM-like neutral scalar $h$ will have an extra invisible decay channel through $h \rightarrow H H$. Taking the Invisible decay branching ratio of the $125$ GeV SM-like Higgs can be as large as ${Br_{inv}}_h < 25 \%$, we have studied the parameter space of the effective coupling $\lambda^*$ between the neutral scalars ($hHH$) and the mass of the DM candidate lighter neutral scalar $m_H$. We also comment on the other possible phenomenology for the charged scalars $H^\pm$ and pseudoscalar $A$.
