Intermediate scales, μ parameter, and fermion masses from string models

We address intermediate scales within a class of string models. The intermediate scales occur due to the SM singlets (Formula presented) acquiring non-zero VEVs due to radiative breaking; the mass squared (Formula presented) of (Formula presented) is driven negative at (Formula presented) due to O(1) Yukawa couplings of (Formula presented) to exotic particles (calculable in a class of string models). The actual VEV of (Formula presented) depends on the relative magnitude of the non-renormalizable terms of the type (Formula presented) in the superpotential. We mainly consider the case in which the (Formula presented) are charged under an additional non-anomalous (Formula presented) gauge symmetry and the VEVs occur along (Formula presented)- and (Formula presented)-flat directions. We explore various scenarios in detail, depending on the type of Yukawa couplings to the exotic particles and on the initial boundary values of the soft SUSY breaking parameters. We then address the implications of these scenarios for the μ parameter and the fermionic masses of the standard model.