Successful Yukawa structures in Warped Extra Dimensions

Abstract

For a RS model, with SM fields in the bulk and the Higgs boson on the TeV-brane, we suggest two specific structures for the Yukawa couplings, one based on a permutation symmetry and the other on the Universal Strength of Yukawa couplings hypothesis (USY). In USY, all Yukawa couplings have equal strength and the difference in the Yukawa structure lies in some complex phase. In both scenarios, all Yukawa couplings are of the same order of magnitude. Thus, the main features of the fermion hierarchies are explained through the RS geometrical mechanism, and not because some Yukawa coupling is extremely small. We find that the RS model is particularly appropriate to incorporate the suggested Yukawa configurations. Indeed, the RS geometrical mechanism of fermion locations along the extra dimension, combined with the two Yukawa scenarios, reproduces all the present experimental data on fermion masses and mixing angles. It is quite remarkable that in the USY case, only two complex phases of definite value +-Pi/2 are sufficient to generate the known neutrino mass differences, while at same time, permitting large leptonic mixing in agreement with experiment.