Higgs scalers in the minimal nonminimal supersymmetric standard model

We consider the simplest and most economic version among the proposed nonminimal supersymmetric models, in which the mu parameter is promoted to a singlet superfield, whose self-couplings are all absent from the renormalizable superpotential. Such a particularly simple form of the renormalizable superpotential may be enforced by discrete R symmetries which are extended to the gravity-induced nonrenormalizable operators as well. We show explicitly that within the supergravity-mediated supersymmetry-breaking scenario, the potentially dangerous divergent tadpoles associated with the presence of the gauge singlet first appear at loop levels higher than 5 and therefore do not destabilize the gauge hierarchy. The model provides a natural explanation for the origin of the mu term, without suffering from the visible axion or the cosmological domain-wall problem. Focusing on the Higgs sector of this minimal nonminimal supersymmetric standard model, we calculate its effective Higgs potential by integrating out the dominant quantum effects due to top squarks. We then discuss the phenomenological implications of the Higgs scalars predicted by the theory for the present and future high-energy colliders. In particular, we find that our new minimal nonminimal supersymmetric model can naturally accommodate a relatively light charged Higgs boson, with a mass close to the present experimental lower bound.