Fermion masses and mixing in intersecting brane scenarios

We study the structure of Yukawa couplings in intersecting D6-branes wrapping a factorizable 6-torus compact space $T^6.$ Models with a MSSM-like spectrum are analyzed and found to fail in predicting the quark mass spectrum because of the way in which the family structures for the left-handed, right-handed quarks, and, eventually, the Higgs fields are “factorized” among the different tori. In order to circumvent this, we present a model with three supersymmetric Higgs doublets which satisfies the anomaly cancellation condition in a more natural way than the previous models, where quarks were not treated universally regarding their brane assignments or some particular branes were singled out, being invariant under orientifold projection. In our model, the family structures of all standard model particles arise in one of the tori and can naturally lead to universal strength Yukawa couplings which accommodate the quark mass hierarchy and mixing angles.