Ultra Visible Warped Model From Flavor Triviality & Improved Naturalness

TL;DR

The paper investigates a warped 5D model where Yukawa hierarchies are UV-driven and flavor is governed by an MFV-like bulk symmetry, yielding a bulk Rattazzi–Zaffaroni (RZ) framework with suppressed flavor violation. It demonstrates a sweet-spot region in parameter space where the Kaluza–Klein scale can be as low as $m_{ m KK} \approx 2$ TeV while remaining consistent with electroweak precision tests (EWPTs) and flavor constraints, aided by a bulk Higgs that makes the $S$ parameter one-loop finite. The scenario predicts TeV-scale flavor gauge bosons and potentially sizable CP violation in $\Delta B=2$ transitions, with a characteristic depletion of third-generation couplings in line with minimal flavor violation, and CPV patterns that could accommodate Tevatron hints for $B_s$ mixing. Overall, the model offers improved naturalness relative to anarchic RS models and enhanced prospects for LHC discovery, while remaining compatible with current flavor and EW data.

Abstract

A warped extra-dimensional model, where the Standard Model Yukawa hierarchy is set by UV physics, is shown to have a sweet spot of parameters with improved experimental visibility and possibly naturalness. Upon marginalizing over all the model parameters, a Kaluza-Klein scale of 2.1 TeV can be obtained at 2 sigma (95.4 CL) without conflicting with electroweak precision measurements. Fitting all relevant parameters simultaneously can relax this bound to 1.7 TeV. In this bulk version of the Rattazzi-Zaffaroni shining model, flavor violation is also highly suppressed, yielding a bound of 2.4 TeV. Non-trivial flavor physics at the LHC in the form of flavor gauge bosons is predicted. The model is also characterized by a depletion of the third generation couplings -- as predicted by the general minimal flavor violation framework -- which can be tested via flavor precision measurements. In particular, sizable CP violation in Delta B=2 transitions can be obtained, and there is a natural region where Bs mixing is predicted to be larger than Bd mixing, as favored by recent Tevatron data. Unlike other proposals, the new contributions are not linked to Higgs or any scalar exchange processes.

Figures (6)

• Figure 1: Tree diagrams contributing at leading order to the EWPO. The double line denotes a sum over the various gauge KK-states, while the cross represents KK/zero-mode mixing from the Higgs VEV. $W^a_{0}$ are the SM zero-modes with $a=0,\dots,3$ and $W^0\equiv B$ is the hypercharge gauge field.
• Figure 2: Diagram contributing to the SM gauge boson propagators at one-loop.
• Figure 3: One-loop diagrams contributing to $Zb_L\bar{b}_L$ in the unitary gauge. KK-modes of third generation $Q=2/3$ states and $W^\pm$ zero-mode are running in the loop.
• Figure 4: Two-loop diagram relevant for matching onto the dimension-six operator generating the $S$ parameter. A similar diagram with exchange of weak gauge boson is also present.
• Figure 5: $\chi^2 - \chi^2_{SM}$ as a function of $c_{U^i}$, with the rest of the parameters fixed to the best fit values of Eq. (\ref{['bestfit']}). Besides being relatively insensitive to the localization of $U^i$, the $\chi^2$ distribution flattens for $c_{U^i}<-0.5$. Here we take $m_{H} = 115~{\rm GeV}$.