Broken Supersymmetric U(1) Gauge Factor at the TeV Scale

The appearance of a broken supersymmetric U(1) gauge factor at the TeV scale is relevant for several reasons. If it truly exists, then one important consequence is that at the 100 GeV energy scale, the two-doublet Higgs structure is of a more general form than that of the Minimal Supersymmetric Standard Model (MSSM). This is a prime example of tree-level nondecoupling. Furthermore, a particular U(1)_N from the superstring-inspired E_6 model allows for the existence of naturally light singlet neutrinos which may be necessary to accommodate the totality of neutrino-oscillation experiments.