[Formula Presented] in the two-Higgs-doublet model

We compute the cross section for [Formula Presented] in the general CP-conserving type-II two-Higgs-doublet model. We sum the contributions from the “t-channel” [Formula Presented] graphs and “s-channel” [Formula Presented] graphs, including their interference. Higgs-triangle graphs and all box diagrams are included. For many parameter choices, especially those in the decoupling region of parameter space (light [Formula Presented] and [Formula Presented] the Higgs-triangle and box diagrams are found to be of minor importance, the main contributing loops being the top and bottom quark triangle diagrams. The predicted cross section is rather small for [Formula Presented] and/or [Formula Presented] However, we also show that if parameters are chosen corresponding to large Higgs self-couplings then the Higgs-triangle graphs can greatly enhance the cross section. We also demonstrate that the supersymmetry-loop corrections to the [Formula Presented] coupling could be such as to greatly enhance this coupling, resulting in an enhanced [Formula Presented] cross section. Complete cross-section expressions are given in the Appendixes.