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 μ-term, and the effect of higher-order terms.