CP and Flavour in Effective Type I String Models

Abstract

Effective type I string models allow stabilization of the dilaton and moduli fields with only a single gaugino condensate. We show that, as well as breaking supersymmetry, the stabilization can spontaneously break CP. We find that this source of CP violation hints strongly at a natural solution to the supersymmetric CP and flavour problems. Even though the CP violation generates physical phases in the Yukawa couplings, all the supersymmetry breaking terms are found to be automatically real and given by the U(1) charges of the associated Yukawa couplings. These can be chosen to have a structure (degenerate or non-universal) which suppresses FCNCs and EDMs. We examine the phenomenological implications, including the generation of the $\mu$-term, and the effect of higher order terms.