LAUSR

The one-loop contributions to the decays of the CP -odd and CP -even scalar bosons A→ Zγγ and φ → Zγγ (φ = 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→ Zγγ branching ratio is only relevant when mA > mH +mZ , but it is negligible otherwise. For mA > 600 GeV and tβ ' O(1), BR(A → Zγγ) can reach values of the order of 10−5 − 10−4, but it decreases by about one order of magnitude as tβ increases up to 10. A similar behavior is followed by the H → Zγγ decay, which only has a non-negligible branching ratio when mH > mA + mZ and can reach the level of 10−4 − 10−3 for mH > 600 GeV and tβ ' O(1). We also estimated the branching ratios of these rare decays in the type-I THDM, where they can be about one order of magnitude larger than in type-II THDM. As far as the h → Zγγ decay is concerned, since the properties of this scalar boson must be nearly identical to those of the SM Higgs boson, the h→ Zγγ 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.