Sources of CP violation in the two-Higgs-doublet model.

Assuming $\mathrm{CP}$ violation arises solely through the Higgs potential, we develop the most general two-Higgs-doublet model. There is no discrete symmetry that distinguishes the two Higgs bosons. It is assumed that an approximate global family symmetry sufficiently suppresses flavor-changing neutral scalar interactions. In addition to a Cabibbo-Kobayashi-Maskawa phase, neutral boson mixing, and superweak effects, there can be significant $\mathrm{CP}$ violation due to charged Higgs boson exchange. The value of $\frac{{\ensuremath{\epsilon}}^{\ensuremath{'}}}{\ensuremath{\epsilon}}$ due to this last effect could be as large as in the standard model.