Effective two Higgs doublets in nonminimal supersymmetric models

The Higgs sectors of supersymmetric extensions of the Standard Model have two doublets in the minimal version (MSSM), and two doublets plus a singlet in two others: with (UMSSM) and without (NMSSM) an extra U(1)′. A very concise comparison of these three models is possible if we assume that the singlet has a somewhat larger breaking scale compared to the electroweak scale. In that case, the UMSSM and the NMSSM become effectively two-Higgs-doublet models (THDM), like the MSSM. In this approach the well-known upper mass bounds on the lightest CP-even neutral Higgs boson can be derived in a very simple and transparent way.