Decoupling Supersymmetry/Higgs without fine-tuning

We propose a simple superpotential for the Higgs doublets, where the electroweak symmetry is broken at the supersymmetric level. We show that, for a class of supersymmetry breaking scenarios, the electroweak scale can be stable even though the supersymmetry breaking scale is much higher than it. Therefore, all the superpartners and the Higgs bosons can be decoupled from the electroweak scale, nevertheless no fine-tuning is needed. We present a concrete model, as an existence proof of such a model, which generates the superpotential dynamically. According to supersymmetry breaking scenarios to be concerned, various phenomenological applications of our model are possible. For example, based on our model, the recently proposed ``split supersymmetry'' scenario can be realized without fine-tuning. If the electroweak scale supersymmetry breaking is taken into account, our model provides a similar structure to the recently proposed ``fat Higgs'' model and the upper bound on the lightest Higgs boson mass can be relaxed.