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We present a variant of the warped extra dimension, Randall-Sundrum (RS), framework which is based on five dimensional (5D) minimal flavor violation (MFV), in which the only sources of flavor breaking are two 5D anarchic Yukawa matrices. The Yukawa matrices also control the bulk masses, which are responsible for the resulting flavor structure and mass hierarchy in the low energy theory. An interesting result of this set-up is that at low energies the theory flows to next to MFV model where flavor violation is dominantly coming from the third generation. Low energy flavor violation is further suppressed by a single parameter that dials the amount of violation in the up or down sector. There is therefore a sharp limit in which there is no flavor violation in the down type quark sector which, remarkably, is favored when we fit for the flavor parameters. This mechanism is used to eliminate the current RS flavor and CP problem even with a Kaluza-Klein scale as low as 2 TeV! Our construction also suggests that economic supersymmetric and non-supersymmetric, strong dynamic-based, flavor models may be built based on the same concepts.
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Randall Sundrum models provide a possible explanation of (gauge-gravity) hierarchy, whereas discrete symmetry flavor groups yield a possible description of the texture of Standard Model fermion masses. We use both these ingredients to propose a five-dimensional extension of the Standard Model where the mass hierarchy of the four-dimensional effective field theory is obtained only using localizations parameters of order 1. We consider a bulk custodial gauge symmetry group together with an Abelian $Z_4$ group: the model turns out to yield a rather minimal extension of the SM as it only requires two brane Higgs fields to provide the desired Yukawa interactions and the required spontaneous symmetry breaking pattern. In fact, the presence of an extra-dimension allows the use of the Scherk-Schwarz mechanism to contribute to the breaking of the bulk custodial group down to the SM gauge symmetry. Moreover, no right-handed neutrinos are present and neutrino masses are generated radiatively with the help of a bulk charged scalar field that provides the Lepton-number violation. Using experimental inputs from the Global Neutrino Analysis and recent Daya Bay results, a numerical analysis is performed and allowed parameter regions are displayed.
We propose a simple and predictive model of fermion masses and mixing in a warped extra dimension, with the smallest discrete non-Abelian group $S_{3}$ and the discrete symmetries $Z_{2}otimes Z_{4}$. Standard Model fields propagate in the bulk and the mass hierarchies and mixing angles are accounted for the fermion zero modes localization profiles, similarly to the the Randall-Sundrum (RS) model. To the best of our knowledge, this model is the first implementation of an $S_{3}$ flavor symmetry in this type of warped extra dimension framework. Our model successfully describes the fermion masses and mixing pattern and is consistent with the current low energy fermion flavor data. The discrete flavor symmetry in our model leads to predictive mixing inspired textures, where the Cabbibo mixing arises from the down type quark sector whereas up type quark sector contributes to the remaining mixing angles.
We explore realizations of minimal flavor violation (MFV) for leptons in the simplest seesaw models where the neutrino mass generation mechanism is driven by new fermion singlets (type I) or triplets (type III) and by a scalar triplet (type II). We also discuss similarities and differences of the MFV implementation among the three scenarios. To study the phenomenological implications, we consider a number of effective dimension-six operators that are purely leptonic or couple leptons to the standard-model gauge and Higgs bosons and evaluate constraints on the scale of MFV associated with these operators from the latest experimental information. Specifically, we employ the most recent measurements of neutrino mixing parameters as well as the currently available data on flavor-violating radiative and three-body decays of charged leptons, mu -> e conversion in nuclei, the anomalous magnetic moments of charged leptons, and their electric dipole moments. The most stringent lower-limit on the MFV scale comes from the present experimental bound on mu -> e gamma and can reach 500 TeV or higher, depending on the details of the seesaw scheme. With our numerical results, we illustrate some important differences among the seesaw types. In particular, we show that in types I and III there are features which can bring about potentially remarkable effects which do not occur in type II. In addition, we comment on how one of the new effective operators can induce flavor-changing dilepton decays of the Higgs boson, which may be probed in upcoming searches at the LHC.
We study the flavor changing neutral current decays of the MSSM Higgs bosons into strange and bottom quarks. We focus on a scenario of minimum flavor violation here, namely only that induced by the CKM matrix. Taking into account constraint from $bto s gamma$, $deltarho$ as well as experimental constraints on the MSSM spectrum, we show that the branching ratio of $(Phito bbar{s})$ and $(Phi to bar{b}s)$ combined, for $Phi$ being either one of the CP even Higgs states, can reach the order $10^{-4}$-$10^{-3}$ for large $tanbeta$, large $mu$, and large $A_t$. The result illustrates the significance of minimal flavor violation scenario which can induce competitive branching fraction for flavor changing Higgs decays. This can be compared with the previous studies where similar branching fraction has been reported, but with additional sources of flavor violations in squark mass matrices. We also discuss some basic features of the flavor violating decays in the generic case.
We study a mechanism, inspired from the mechanism for generating the gauge hierarchy in Randall-Sundrum model, to investigate the cosmological constant problem. First we analyze the bulk cosmological constant and brane vacuum energies in RS model. We show that the five-dimensional bulk cosmological constant and the vacuum energies of the two branes all obtain their natural values. Finally we argue how we can generate a small four-dimensional effective cosmological constant on the branes through modifying the original RS model.
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