Simple flavor protection for the Randall-Sundrum model

Abstract

We present a simple variation of warped flavor models where the hierarchies of fermion masses and mixings are still explained but dangerous flavor-violating effects in the Kaon sector are greatly reduced. The key new ingredients are two horizontal $U(1)$ symmetries. These symmetries forbid flavor violation in the down-quark sector (with the exception of IR brane localized kinetic mixing terms for the left-handed quarks) while allowing for flavor violation in the up-quark sector. The leading flavor constraints come from ${D}^{0}\ensuremath{-}{\overline{D}}^{0}$ mixing, and are safely satisfied for the Kaluza-Klein mass scale of order 3 TeV. Our analysis of the flavor constraints includes the effects of the (usually ignored) brane localized kinetic terms. We also comment on the effects of the additional $U(1)$ gauge bosons that are present if the horizontal symmetries are gauged.