Orbifold-induced $\mu$ term and electroweak symmetry breaking
  It is known that a Higgs $\mu$ term can be naturally generated through the K\"ahler potential in orbifold string models in which one of the three compactified complex planes has order two. In this class of models explicit expressions for both the $\mu$ parameter and the soft SUSY-breaking parameters can be obtained under the assumption that the goldstino is an arbitrary linear combination of the fermionic partners of the dilaton $S$ and all the moduli $T_i,U_i$. We apply this picture to the MSSM and explore the consistency of the obtained boundary conditions with radiative gauge symmetry breaking. We find that consistency with the measured value of the top-quark mass can only be achieved if the goldstino has a negligible dilatino component and relevant components along the $T_3,U_3$ moduli associated to the order-two complex plane. 
A. Brignole, L.E. Ib\'a\~nez and C. Mu\~noz