Pseudoscalar Higgs Boson Decays into W and Z Bosons Revisited

We examine, in a number of Standard Model extensions, whether the decays $A \to WW/ZZ$ of a neutral pseudoscalar (Higgs) resonance can have branching ratios at the percent level and we determine the possible size of $B(A \to WW/ZZ)$ relative to the respective branching ratios of a scalar boson $H$. The branching ratios of the these decay modes and the total widths $\Gamma_A$, $\Gamma_H$ are computed in the minimal supersymmetric extension of the SM, in a type-II two-Higgs doublet extension (2HDM), in a 2HDM with 4 chiral fermion generations, in a 2HDM with additional heavy vector-like quarks, and in a top-color assisted technicolor model. We find that in the above non-supersymmetric models $B(A \to WW)$ can be about 2%, while $B(A \to ZZ) \lesssim 10^{-3}.$ The ratio $B(A \to WW)/B(H \to WW)$ can be of order 10% in large regions of the parameter space of the models.