THE MU-TERM IN EFFECTIVE SUPERGRAVITY THEORIES

The Higgs mixing term coefficient mu(eff) is calculated in the scalar potential in supergravity theories with string origin, in a model inde pendent approach. A general low energy effective expression is derived , where new contributions are included which depend on the modular wei ghts q(1,2) of the Higgs superfields, the moduli and derivative terms. We find that in a class of models obtained in the case of compactific ations of the heterotic superstring, the derivative terms are identica lly zero. Further, the total mu(eff)-term vanishes identically if the sum of the two modular weights q(1) + q(2) is equal to two. Subleading mu-corrections, in the presence of intermediate gauge symmetries pred icted in viable string scenarios, are also discussed.