Flavor Structure of Warped Extra Dimension Models

TL;DR

This paper analyzes the flavor structure of warped extra dimension models with bulk custodial symmetry, focusing on TeV-scale KK masses. Using a spurion framework, it shows that zero-mode profiles dominate flavor, yielding robust, model-independent predictions across a class of RS1-like constructions and predicting detectable NP in $\Delta F=2$, $\Delta F=1$, and dipole processes, with EDMs posing a CP problem at $m_{KK}\sim 3$ TeV. The authors connect the 5D picture to a 4D CFT dual, arguing that the flavor structure mirrors composite-Higgs dynamics and operator mixing, and they discuss correlations that link low-energy flavor observables to high-energy KK couplings. The findings motivate targeted B-physics and rare-decay tests, while highlighting a tension between KK scales, CP violation, and EW precision constraints that can be alleviated by heavier KK masses or bulk Higgs configurations.

Abstract

We recently showed, in hep-ph/0406101, that warped extra dimensional models with bulk custodial symmetry and few TeV KK masses lead to striking signals at $B$-factories. In this paper, using a spurion analysis, we systematically study the flavor structure of models that belong to the above class. In particular we find that the profiles of the zero modes, which are similar in all these models, essentially control the underlying flavor structure. This implies that our results are robust and model independent in this class of models. We discuss in detail the origin of the signals in B-physics. We also briefly study other NP signatures that arise in rare K decays ($K \to πνν$), in rare top decays [$t \to c γ(Z, gluon)$] and the possibilty of CP asymmetries in $D^0$ decays to CP eigenstates such as $K_S π^0$ and others. Finally we demonstrate that with light KK masses, $\sim3$ TeV, the above class of models with anarchic $5D$ Yukawas has a ``CP problem'' since contributions to the neutron electric dipole moment are roughly 20 times larger than the current experimental bound. Using AdS/CFT correspondence, these extra-dimensional models are dual to a purely 4D strongly coupled conformal Higgs sector thus enhancing their appeal.