Mass Terms in Two-Higgs Doublet Models

We take a closer look at the mass terms of all renormalizable and CP conserving two-Higgs doublet models (THDM). We show that some of the dimension two parameters in the potential can be set equal to zero leading to relations among the tree-level parameters of the potential. This means that the number of tree-level free parameters can be reduced from seven to six or even five without spoiling the renormalizability of the model. Hence, the minimal version of a renormalizable and CP conserving THDM is in fact a class of models differing from each other by tree-level relations among the parameters. The different versions of the THDM give rise to different amplitudes for physical processes. We will illustrate this with two examples. The first one is the one-loop weak correction to the top decay width, t -> b W. The second one is the decay h -> gamma gamma in the fermiophobic limit