Perturbative unification of gauge couplings in supersymmetric E6 models

We study gauge coupling unification in supersymmetric (SUSY) E-6 models where an additional U(1)' gauge symmetry is broken near the TeV scale and a number of exotic matter fields from the 27 representations have O(TeV) mass. Solving the two-loop renormalization group equations (RGE) of gauge couplings and a kinetic mixing coupling between the U(1)' and U(1)(Y) gauge fields, we find that the gauge couplings fall into the non-perturbative regime below the grand unified theories (GUT) scale. We examine threshold corrections on the running of gauge couplings from both light and heavy (similar to GUT scale) particles and show constraints on the size of corrections to achieve the perturbative unification of gauge couplings.