An Example of Higher Weight Superpotential Interaction in the Heterotic String on Orbifolds

An explicit orbifold example of the non-zero correlation functions related to the additional contribution to the induced mass term for Higgs particles at low energies is given. We verify that they form finite dimensional representations of the target space modular transformation $SL_2(Z)$. This action of the modular group is shown to be consistent with its action on the fixed points set defining the twisted fields.