Models with inverse sfermion mass hierarchy and decoupling of the SUSYFCNCeffects

We study the decoupling of the first two squark and slepton families in ord er to lower the flavour changing neutral current effects. Models with inver se sfermion mass hierarchy based upon gauged U(1) flavour symmetries provid e a natural framework where decoupling can be implemented. Decoupling requi res a large gap between the Fermi scale and the supersymmetry breaking scal e. Maintaining the electroweak symmetry breaking at the Fermi scale require s some fine-tuning that we investigate by solving the two-loop renormalizat ion group equations. We show that the two-loop effects are governed by the anomaly compensated by the Green-Schwarz mechanism and can be determined fr om the quark and lepton masses. The electroweak breaking constraints lead t o a small mu scenario where the LSP is Higgsino-like.