μB-driven Electroweak Symmetry Breaking

We consider a scenario in which the dominant quartic coupling for the Higgs doublets arises from the F -term potential, rather than the conventional SU(2)L × U(1)Y D-term potential, in supersymmetric theories. The quartic coupling arises from a superpotential interaction between the two Higgs doublets and a singlet field, but unlike the case in the next-to-minimal supersymmetric standard model the singlet field is not responsible for the generation of the supersymmetric or holomorphic supersymmetry-breaking masses for the Higgs doublets. We find that this naturally leads to a deviation from the conventional picture of top-Yukawa driven electroweak symmetry breaking — electroweak symmetry breaking is triggered by the holomorphic supersymmetry breaking mass for the Higgs doublets (the μB term). This allows a significant improvement for fine-tuning in electroweak symmetry breaking, since the top squarks do not play a major role in raising the Higgs boson mass or in triggering electroweak symmetry breaking and thus can be light. The amount of fine-tuning is given by the squared ratio of the lightest Higgs boson mass to the charged Higgs boson mass, which can be made better than 20%. Solid implications of the scenario include a small value for tan β, tanβ <∼ 3, and relatively light top squarks.