Fine tuning in the constrained exceptional supersymmetric standard model

Abstract

Supersymmetric unified models in which the Z′ couples to the Higgs doublets, as in the E6 class of models, have large fine tuning dominated by the experimental mass limit on the Z′. To illustrate this, we investigate the degree of fine tuning throughout the parameter space of the constrained exceptional supersymmetric standard model (cE6SSM) that is consistent with a Higgs mass mh∼125 GeV. Fixing tan =10, and taking specific values of the mass of the Z ′ boson, with MZ′∼2-4 TeV, we find that the minimum fine tuning is set predominantly from the mass of Z ′ and varies from ∼200 to 400 as we vary MZ′ from ∼2 to 4 TeV. However, this is significantly lower than the fine tuning in the constrained minimal supersymmetric standard model, of O(1000), arising from the large stop masses required to achieve the Higgs mass. © 2013 American Physical Society.