Realistic anomaly-mediated supersymmetry breaking

We consider supersymmetry breaking communicated entirely by the superconfor mal anomaly in supergravity. This scenario is naturally realized if supersy mmetry is broken in a hidden sector whose couplings to the observable secto r are suppressed by more than powers of the Planck scale, as occurs if supe rsymmetry is broken in a parallel universe living in extra dimensions. This scenario is extremely predictive: soft supersymmetry breaking couplings ar e completely determined by anomalous dimensions in the effective theory at the weak scale. Gaugino and scalar masses are naturally of the same order, and flavor-changing neutral currents are automatically suppressed. The most glaring problem with this scenario is that slepton masses are negative in the minimal supersymmetric standard model. We point out that this problem c an be simply solved by coupling extra Higgs doublets to the leptons. Lepton flavor-changing neutral currents can be naturally avoided by approximate s ymmetries. We also describe more speculative solutions involving compositen ess near the weak scale. We then turn to electroweak symmetry breaking. Add ing an explicit mu term gives a value for B mu that is too large by a facto r of similar to 100. We construct a realistic model in which the mu term ar ises from the vacuum expectation value of a singlet field, so all weak-scal e masses are directly related to m(3/2). We show that fully realistic elect roweak symmetry breaking can occur in this model with moderate fine-tuning.