Gaugino Mediated Supersymemtry Breaking

We consider supersymmetric theories where the standard-model quark and lepton fields are localized on a `3-brane' in extra dimensions, while the gauge and Higgs fields propagate in the bulk. If supersymmetry is broken on another 3-brane, supersymmetry breaking is communicated to gauge and Higgs fields by direct higher-dimension interactions, and to quark and lepton fields via standard-model loops. We show that this gives rise to a realistic and predictive model for supersymmetry breaking. The size of the extra dimensions is required to be of order $10$--$100$ times larger than fundamental scale (\eg~the string scale). The spectrum is similar to (but distinguishable from) the predictions of `no-scale' models. Flavor-changing neutral currents are naturally suppressed. The $\mu$ term can be generated by the Giudice-Masiero mechanism. The supersymmetric CP problem is naturally solved if CP violation occurs only on the observable sector 3-brane. These are the simplest models in the literature that solve all supersymmetric naturalness problems.