Supersymmetric U(1) at the TeV Scale
  If there exists an arbitrary supersymmetric U(1) gauge factor at the TeV scale, under which the two Higgs superfields H_{1,2} of the standard model are nontrivial, and if there is also a singlet superfield S such that the H_1 H_2 S term is allowed in the superpotential, then the structure of the two-doublet Higgs sector at the electroweak scale is more general than that of the MSSM (Minimal Supersymmetric Standard Model). Under further assumptions of grand unification and universal soft supersymmetry breaking terms, the scale of U(1) breaking is related to the parameter tan(beta) = v_2/v_1. 
E. Keith (U of Texas, Austin) and Ernest Ma (UC Riverside)