Improved single sector supersymmetry breaking - art. no. 075006

Building on recent work by Arkani-Hamed and the present authors, we constru ct realistic models that break supersymmetry dynamically and give rise to c omposite quarks and leptons, all in a single strongly coupled sector. The m ost important improvement compared to earlier models is that the second-gen eration composite states correspond to dimension-2 ''meson" operators in th e ultraviolet. This leads to a higher scale for flavor physics and gives a completely natural suppression of flavor-changing neutral currents. We also construct models in which the hierarchy of Yukawa couplings is explained b y the dimensionality of composite states. These models provide an interesti ng and viable alternative to gravity- and gauge-mediated models. The generi c signatures are unification of scalar masses with different quantum number s at the compositeness scale, and lighter gaugino, Higgsino, and third-gene ration squark and slepton masses. We also analyze large classes of models t hat give rise to local vacua with both compositeness and supersymmetry brea king, based on gauge theories with confining, fixed-point, or free-magnetic dynamics.