Improving the Fine Tuning in Models of Low Energy Gauge Mediated Supersymmetry Breaking

Abstract

The fine tuning in models of low energy gauge mediated supersymmetry breaking required to obtain the correct $Z$ mass is quantified. To alleviate the fine tuning problem, a model with split $(5+\bar{5})$ messenger fields is presented. This model has additional triplets in the low energy theory which get a mass of $O(500)$ GeV from a coupling to a singlet. The improvement in fine tuning is quantified and the spectrum in this model is discussed. The same model with the above singlet coupled to the Higgs doublets to generate the $\mu$ term is also discussed. A Grand Unified version of the model is constructed and a known doublet-triplet splitting mechanism is used to split the messenger $(5+\bar{5})$'s. A complete model is presented and some phenomenological constraints are discussed.