THE EXTRA VECTOR ABEYANCE (EVA) MECHANISM AS THE ORIGIN OF THE KM MATRIX

We examine a general mechanism whereby an extra vector-like quark of mass M(eva) generates realistic quark mixing angles from otherwise flavor diagonal quark Yukawa matrices. For scales above M(eva) the vector-like quark is manifest, while the Yukawa matrices are diagonal, i.e., the KM matrix is held in abeyance. Conversely, for scales below M(eva) the vector-like quark is in an abeyant state, while the KM matrix is manifest. This mechanism is naturally realized in many superstring models. In fact, knowledge of the Yukawa matrices at the string scale, together with suitable renormalization group scaling, unambiguously determines the quark mass ratios and the KM angles at low energies. Conversely, these low-energy observable may be used to determine as-yet-unknown parameters in the string model. We explicitly apply the EVA mechanism to a toy model inspired by the structure of the flipped SU (5) string model, to illustrate how this mechanism may be used to predict some of the KM angles. We also outline the procedure to be followed in a realistic calculation in the flipped SU (5) string model.