Simple Scheme for Gauge Mediation

We present a simple scheme for constructing models that achieve successful gauge mediation of supersymmetry breaking. In addition to our previous work [1] that proposed drastically simplified models using metastable vacua of supersymmetry breaking in vector-like theories, we show there are many other successful models using various types of supersymmetry breaking mechanisms that rely on enhanced low-energy U(1)_R symmetries. In models where supersymmetry is broken by elementary singlets, one needs to assume U(1)_R violating effects are accidentally small, while in models where composite fields break supersymmetry, emergence of approximate low-energy U(1)_R symmetries can be understood simply on dimensional grounds. Even though the scheme still requires somewhat small parameters to sufficiently suppress gravity mediation, we discuss their possible origins due to dimensional transmutation. The scheme accommodates a wide range of the gravitino mass to avoid cosmological problems.