Decays $A \to Z\gamma\gamma$ and $\phi \to Z\gamma\gamma$ ($\phi=h,H$) in two-Higgs doublet models.

The one-loop contributions to the decays of the CP-odd and CP-even scalar bosons $A\to Z\gamma\gamma$ and $\phi\to Z\gamma\gamma$ ($\phi=h,H$) are calculated within the framework of CP-conserving THDMs, where they are induced by box and reducible Feynman diagrams. The behavior of the corresponding branching ratios are then analyzed within the type-II THDM in a region of the parameter space around the alignment limit and still consistent with experimental data. It is found that the $A\to Z\gamma\gamma$ branching ratio is only relevant when $m_A>m_H+m_Z$, but it is negligible otherwise. For $m_A>600$ GeV and $t_\beta\simeq O(1)$, $BR(A\to Z\gamma\gamma)$ can reach values of the order of $10^{-5}$, but it decreases by about one order of magnitude as $t_\beta$ increases up to 10. A similar behavior is followed by the $H\to Z\gamma\gamma$ decay, which only has a non-negligible branching ratio when $m_H>m_A+m_Z$ and can reach the level of $10^{-4}$ for $m_H>600$ GeV and $t_\beta\simeq O(1)$. Since the properties of the $h$ scalar boson are nearly identical to the SM Higgs boson, the $h\to Z\gamma\gamma$ branching ratio does not deviates significantly from the SM prediction, where it is negligibly small, of the order of $10^{-9}$. This result is in agreement with previous calculations.