Warped higher-dimensional compactifications with "bulk" standard model, or their AdS/CFT dual as the purely 4D scenario of Higgs compositeness and partial compositeness, offer an elegant approach to resolving the electroweak hierarchy problem as well as the origins of flavor structure. However, low-energy electroweak/flavor/CP constraints and the absence of non-standard physics at LHC Run 1 suggest that a "little hierarchy problem" remains, and that the new physics underlying naturalness may lie out of LHC reach. Assuming this to be the case, we show that there is a simple and natural extension of the minimal warped model in the Randall-Sundrum framework, in which matter, gauge and gravitational fields propagate modestly different degrees into the IR of the warped dimension, resulting in rich and striking consequences for the LHC (and beyond). The LHC-accessible part of the new physics is AdS/CFT dual to the mechanism of "vectorlike confinement", with TeV-scale Kaluza-Klein excitations of the gauge and gravitational fields dual to spin-0,1,2 composites. Unlike the minimal warped model, these low-lying excitations have predominantly flavor-blind and flavor/CP-safe interactions with the standard model. Remarkably, this scenario also predicts small deviations from flavor-blindness originating from virtual effects of Higgs/top compositeness at $\sim O(10)$ TeV, with subdominant resonance decays into Higgs/top-rich final states, giving the LHC an early "preview" of the nature of the resolution of the hierarchy problem. Discoveries of this type at LHC Run 2 would thereby anticipate (and set a target for) even more explicit explorations of Higgs compositeness at a 100 TeV collider, or for next-generation flavor tests.
We study the recently found anomalies in $B$-meson decays within a scenario with a warped extra dimension where the Standard Model fermions are propagating in the bulk. The anomalies are then interpreted as the result of the exchange of heavy vector resonances with electroweak quantum numbers. The model naturally leads to lepton-flavor universality violation when different flavor fermions are differently localized along the extra dimension, signaling a different degree of compositeness in the dual holographic theory.
A realistic five-dimensional warped scenario with all standard model fields propagating in the bulk is proposed. Mass hierarchies would in principle be accounted for by judicious choices of the bulk mass parameters, while fermion mixing angles are restricted by a $Δ(27)$ flavor symmetry broken on the branes by flavon fields. The latter gives stringent predictions for the neutrino mixing parameters, and the Dirac CP violation phase, all described in terms of only two independent parameters at leading order. The scheme also gives an adequate CKM fit and should be testable within upcoming oscilla…
We point out that supersymmetric warped geometry can provide a solution to the SUSY flavor problem, while generating hierarchical Yukawa couplings. In supersymmetric theories in a slice of AdS_5 with the Kaluza-Klein scale M_KK much higher than the weak scale, if all visible fields originate from 5D bulk fields and supersymmetry breaking is mediated by the bulk radion superfield and/or some brane chiral superfields, potentially dangerous soft scalar masses and trilinear $A$ parameters at M_KK can be naturally suppressed compared to the gaugino masses by small warp factor. We present simple mod…
We propose a new flavor paradigm for models with warped extra dimensions. The idea is to impose the minimal amount of flavor protection to make warped models compatible with all current flavor and electroweak precision constraints. We discuss a particular realization of this minimal flavor protection in the quark sector, by means of a flavor symmetry acting on the right handed down sector. Hierarchical quark masses and mixing angles are naturally reproduced through wave function localization, and flavor violating processes are predicted, in the absence of large brane kinetic terms for the righ…
The recent B-meson anomalies are coherently explained at the TeV scale by 4321 gauge models with hierarchical couplings reminiscent of the Standard Model Yukawas. We show that such models arise as the low-energy limit of a complete theory of flavor, based on a warped fifth dimension where each Standard Model family is quasi-localized in a different brane. The Higgs is identified as a pseudo-Nambu-Goldstone boson emerging from the same dynamics responsible for 4321 symmetry breaking. This novel construction unifies quarks and leptons in a flavor non-universal manner, provides a natural descript…
Extra dimensions have interesting consequences for flavor physics. We consider a setup where the standard model fermions and gauge fields reside in the bulk of a warped extra dimension. Fermion masses and mixings are explained by flavor dependent fermion locations, without relying on hierarchical Yukawa couplings. We discuss various flavor violating processes induced by (Kaluza-Klein) gauge boson exchange and non-renormalizable operators. Experimental constraints are satisfied with a Kaluza-Klein scale of about 10 TeV. Some processes, such as muon-electron conversion, are within reach of next …
We consider a five dimensional model with warped geometry where the standard model fermions and gauge bosons correspond to bulk fields. Fermion masses and CKM mixings can be explained in a geometrical picture, without hierarchical Yukawa couplings. We discuss various flavor violating processes induced by (excited) gauge boson exchange and non-renormalizable operators. Some of them, such as muon-electron conversion, are in the reach of next generation experiments.
We propose a model of spontaneous CP violation to address the strong CP problem in warped extra dimensions that relies on sequestering flavor and CP violation. We assume that brane-localized Higgs Yukawa interactions respect a U(3) flavor symmetry that is broken only by bulk fermion mass and Yukawa terms. All CP violation arises from the vev of a CP-odd scalar field localized in the bulk. To suppress radiative corrections to theta-bar, the doublet quarks in this model are localized on the IR brane. We calculate constraints from flavor-changing neutral currents (FCNCs), precision electroweak me…
We review constraints from quark and lepton flavor violation on extra dimensional models with warped geometry, both in the minimal and the custodial model. For both scenarios, KK masses that are large enough to suppress constraints from electroweak precision tests also sufficiently suppress all quark flavor and CP violation, with the exception of CP violation in $K\bar K$ mixing and (to a lesser extend) in $D\bar D$ mixing. In the lepton sector the minimal scenario leads to excessively large contributions to $μ\to eγ$ transitions, requiring KK masses of at least 20 TeV or larger.
We analyze the flavor violation in warped extra dimension due to radion mediation. We show that ΔS=2 and ΔB=2 flavor violating processes impose stringent constraints on radion mass, m_ϕand the scale Λ_ϕ. In particular, for Λ_ϕ~ O(1) TeV, B_d^0-\bar{B}^0_d implies that m_ϕ~ 65 GeV. We also study radion contributions to lepton flavor violating processes: τ-> (e,μ) ϕ, τ-> eμ^+μ^- and B -> l_i l_j. We show that BR(B_s -> μ^+ μ^-) can be of order 10^{-8}, which is reachable at the LHCb. The radion search at LHC, through the flavor violation decays into τμor top-charm quarks, is also considered.
We analyze fermion masses and mixing in a general warped extra dimensional model, where all the Standard Model (SM) fields, including the Higgs, are allowed to propagate in the bulk. In this context, a slightly broken flavor symmetry imposed universally on all fermion fields, without distinction, can generate the full flavor structure of the SM, including quarks, charged leptons and neutrinos. For quarks and charged leptons, the exponential sensitivity of their wave-functions to small flavor breaking effects yield naturally hierarchical masses and mixing as it is usual in warped models with fe…
We study flavor changing neutral current decays of the top quark in the context of general warped extra dimensions, where the five dimensional metric is slightly modified from 5D anti-de-Sitter (AdS$_5$). These models address the Planck-electroweak hierarchies of the Standard Model $and$ can obey all the low energy flavor bounds and electroweak precision tests, while allowing the scale of new physics to be at the TeV level, and thus within the reach of the LHC at Run II. We perform the calculation of these exotic top decay rates for the case of a bulk Higgs, and thus include in particular the …
We propose a scenario which accommodates all the masses and mixings of the SM fermions in a model of warped extra-dimensions with all matter fields in the bulk. In this scenario, the same flavor symmetric structure is imposed on all the fermions of the Standard Model (SM), including neutrinos. Due to the exponential sensitivity on bulk fermion masses, a small breaking of the symmetry can be greatly enhanced and produce seemingly un-symmetric hierarchical masses and small mixing angles among the charged fermion zero-modes (SM quarks and charged leptons) and wash-out the obvious effects of the s…
We consider a 5D warped scenario with a KK-parity symmetry, where the non-trivial warping arises from the dynamics that stabilizes the size of the extra dimension. Generically, the lightest Kaluza-Klein (KK) particle is the first excitation of the radion field, while the next-to-lightest Kaluza-Klein particle is either the first excitation of the (RH) top quark or the first KK-parity odd Higgs. All these masses are expected to be of order the electroweak scale. We present simple analytical expressions for the masses and wavefunctions of the lowest lying KK modes, and derive the Feynman rules n…
Here we study the pattern of neutrino oscillations emerging from a previously proposed warped model construction incorporating $Δ(27)$ flavor symmetry. In addition to a complete description of fermion masses, the model predicts the lepton mixing matrix in terms of two parameters. The good measurement of $θ_{13}$ makes these two parameters nearly proportional, leading to an approximate one-parameter description of neutrino oscillations. There is a sharp fourfold degenerate correlation between $δ_{CP}$ and the atmospheric mixing angle $θ_{23}$, so that maximal $θ_{23}$ also implies maximal lepto…
We study top quark flavor violation in the framework of a warped extra dimension with the Standard Model (SM) fields propagating in the bulk. Such a scenario provides solutions to both the Planck-weak hierarchy problem and the flavor puzzle of the SM without inducing a flavor problem. We find that, generically, tcZ couplings receive a huge enhancement, in particular the right handed ones can be O(1%). This results in BR(t -> c Z) at or above the sensitivity of the Large Hadron Collider (LHC). At the International Linear Collider (ILC), single top production, via e^+ e^- -> t \bar c, can be a s…
The aim of these proceedings is to present the main predictions of the Randall-Sundrum model with custodial protection for particle-antiparticle mixing and rare decays of K and B_(s,d) mesons, putting particular attention on the testability of the resulting NP effects at future experiments. Before giving numerical results, we discuss theoretical expectations, residing in the flavor structure of the model. The high energy scale M_KK is chosen in such a way that direct searches of new particles at the LHC are possible, still being consistent with electroweak precision observables.
A minimal solution to the flavor problem of warped extra-dimension models, i.e. the excessive mixed-chirality contribution to CP violation in K-Kbar mixing arising from Kaluza-Klein (KK) gluon exchange, is proposed. Extending the strong-interaction gauge group in the bulk by an additional SU(3), and breaking this symmetry to QCD via boundary conditions, the constraints arising from the epsilon_K parameter are significantly relaxed. As a result, KK scales M_KK ~ 2 TeV are consistent with all flavor observables without significant fine-tuning. The model predicts the existence of an extended Higg…
We examine various possibilities for realistic 5D higgsless models and construct a full quark sector featuring next-to-minimal flavor violation (with an exact bulk SU(2) protecting the first two generations) satisfying electroweak and flavor constraints. The "new custodially protected representation" is used for the third generation to protect the light quarks from flavor violations induced due to the heavy top. A combination of flavor symmetries, and RS-GIM for the right-handed quarks suppresses flavor-changing neutral currents below experimental bounds, assuming CKM-type mixing on the UV bra…
We propose a spontaneous A4 flavor symmetry breaking scheme implemented in a warped extra dimensional setup to explain the observed pattern of quark and lepton masses and mixings. The main advantages of this choice are the explanation of fermion mass hierarchies by wave function overlaps, the emergence of tribimaximal neutrino mixing and zero quark mixing at the leading order and the absence of tree-level gauge mediated flavor violations. Quark mixing is induced by the presence of bulk flavons, which allow for cross-brane interactions and a cross-talk between the quark and neutrino sectors, re…
We demonstrate that flavor symmetries in warped geometry can provide a natural explanation for large mixing angles and economically explain the distinction between the quark and lepton flavor sectors. We show how to naturally generate Majorana neutrino masses assuming a gauged a U(1)_{B-L} symmetry broken in the UV that generates see-saw masses of the right size. This model requires lepton minimal flavor violation (LMFV) in which only Yukawa matrices (present on the IR brane) break the flavor symmetries. The symmetry-breaking is transmitted to charged lepton bulk mass parameters as well to gen…
We show that CP asymmetries in $b\to s$ hadronic decays are potentially affected by the presence of massive color-octet particles strongly coupled to the third generation quarks. Theories with warped extra dimensions provide natural candidates in the Kaluza-Klein excitations of gluons in scenarios where flavor-breaking by bulk fermion masses results in the localization of fermion wave-functions. Topcolor models, in which a new gauge interaction leads to top-condensation and a large top mass, also result in the presence of these color-octet states with TeV masses . We find that large effects ar…
Warped 5-dimensional models, based on the original Randall-Sundrum geometry, have been extended beyond their initial purpose of resolving the gauge hierarchy problem. Over the past decade, various ingredients have been added to their basic structure in order to provide natural and predictive models of flavor and also to address existing constraints from precision data. In this review, we examine the theoretical and experimental status of realistic models that accommodate current data, while addressing the hierarchy and flavor puzzles of the Standard Model. We also discuss the prospects for fut…
We calculate the production and decay rates of the Higgs boson at the LHC in the context of general 5 dimensional (5D) warped scenarios with a spacetime background modified from the usual $AdS_5$, with SM fields propagating in the bulk. We extend previous work by considering the full flavor structure of the SM, and thus including all possible flavor effects coming from mixings with heavy fermions. We proceed in three different ways, first by only including two complete Kaluza-Klein (KK) levels ($15\times15$ fermion mass matrices), then including three complete KK levels ($21\times21$ fermion m…
We recently proposed a spontaneous A4 flavor symmetry breaking scheme implemented in a warped extra dimensional setup to explain the observed pattern of quark and lepton masses and mixings. The quark mixing is induced by bulk A4 flavons mediating "cross-brane" interactions and a "cross-talk" between the quark and neutrino sectors. In this work we explore the phenomenology of RS-A4 and systematically obtain bounds on the Kaluza-Klein (KK) mass scale implied by flavor changing neutral current (FCNC) processes. In particular, we study the constraints arising from Re(ε'/ε_K), b->sγ, the neutron ED…
In order to explain the non-hierarchical neutrino mixing angles and the absence of lepton flavor violating processes in the context of warped extra dimensions one needs to introduce bulk flavor symmetries. We present a simple model of lepton masses and mixings in RS models based on the A4 non-abelian discrete symmetry. The virtues of this choice are: (i) the natural appearance of the tri-bimaximal mixing pattern; (ii) the complete absence of tree-level flavor violations in the neutral sector; (iii) the absence of flavor gauge bosons; (iv) the hierarchies in the charged lepton masses are explai…
We consider direct experimental verification of warped models, based on the Randall-Sundrum (RS) scenario, that explain gauge and flavor hierarchies, assuming that the gauge fields and fermions of the Standard Model (SM) propagate in the 5D bulk. Most studies have focused on the bosonic Kaluza Klein (KK) signatures and indicate that discovering gauge KK modes is likely possible, yet challenging, while graviton KK modes are unlikely to be accessible at the LHC, even with a luminosity upgrade. We show that direct evidence for bulk SM fermions, {\it i.e.} their KK modes, is likely also beyond the…
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.…
We explore the limits on lepton-flavor universality (LFU) violation in theories where the hierarchy problem is solved by means of a warped extra dimension. In those theories LFU violation, in fermion interaction with Kaluza-Klein modes of gauge bosons, is provided ab initio when different flavor of fermions are differently localized along the extra dimension. As this fact arises from the mass pattern of quarks and leptons, LFU violation is natural in this class of theories. We analyze the experimental data pointing towards LFU violation, as well as the most relevant electroweak and flavor obse…
Anarchic warped extra dimensional models provide a solution to the hierarchy problem. They can also account for the observed flavor hierarchies, but only at the expense of little hierarchy and CP problems, which naturally require a Kaluza-Klein (KK) scale beyond the LHC reach. We have recently shown that when flavor issues are decoupled, and assumed to be solved by UV physics, the framework's parameter space greatly opens. Given the possibility of a lower KK scale and composite light quarks, this class of flavor triviality models enjoys a rather exceptional phenomenology, which is the focus of…
We study radion phenomenology in the context of flavor shining in warped extra dimension models. In this unique setup, originally proposed by Rattazzi and Zaffaroni, solutions to the gauge hierarchy problem and the new physics flavor problem are unified. A special role is played by the vacuum energy on the branes, that naturally allows for flavon stabilization and parametrically raises the radion mass. We note that the radion mass squared is suppressed only by the log of the weak-Planck hierarchy, and it is in the favored range of the standard model Higgs. We emphasize that the radion to di-ph…
We study flavor violation in the quark sector in a purely 4D, two-site effective field theory description of the Standard Model and just their first Kaluza-Klein excitations from a warped extra dimension. The warped 5D framework can provide solutions to both the Planck-weak and flavor hierarchies of the SM. It is also related (via the AdS/CFT correspondence) to partial compositeness of the SM. We focus on the dominant contributions in the two-site model to two observables which we argue provide the strongest flavor constraints, namely, epsilon_K and BR(b -> s gamma), where contributions in the…
We present a warped extra dimension model with the custodial symmetry $SU(2)_L\times SU(2)_R\times U(1)_X\times P_{LR}$ based on the flavor symmetry $S_4\times Z_2\times Z'_2$, and the neutrinos are taken to be Dirac particles. At leading order, the democratic lepton mixing is derived exactly, and the high dimensional operators introduce corrections of order $λ_c$ to all the three lepton mixing angles such that agreement with the experimental data can be achieved. The neutrino mass spectrum is predicted to be of the inverted hierarchy and the second octant of $θ_{23}$ is preferred. We suggest …
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…
In an attempt to simultaneously explain the observed masses and mixing patterns of both quarks and leptons, we recently proposed a model (JHEP08(2010)115) based on the non abelian discrete flavor group A4, implemented in a custodial RS setup with a bulk Higgs. We showed that the standard model flavor structure can be realized within the zero mode approximation (ZMA), with nearly tribimaximal (TBM) neutrino mixing and a realistic CKM matrix with rather mild assumptions. An important advantage of this framework with respect to flavor anarchic models is the vanishing of the dangerous tree level K…
Extensions of the Standard Model featuring a warped extra dimension compactified on an $S^1/\mathbb{Z}_2$ orbifold, in which the fermions and gauge bosons live in the bulk of the fifth dimension, offer one of the most compelling mechanisms for addressing both the hierarchy problem and the flavor puzzle of the Standard Model. However, the five-dimensional mass terms of bulk fermions must be odd functions on the orbifold, and as such they should be described by a field depending on the coordinate of the extra dimension. We demonstrate the feasibility of dynamically generating these fermion bulk …
We calculate the production rate of the Higgs boson at the LHC in the context of general 5 dimensional (5D) warped scenarios with spacetime background modified from the usual $AdS_5$, and where all the SM fields, including the Higgs, propagate in the bulk. This modification can alleviate considerably the bounds coming from precision electroweak tests and flavor physics. We evaluate the Higgs production rate and show that it is generically consistent with the current experimental results from the LHC for Kaluza-Klein (KK) masses as low as 2 TeV, unlike in pure $AdS_5$ scenarios, where for the s…
We have considered a general 5D warped model with SM fields propagating in the bulk and computed explicit expressions for oblique and non-oblique electroweak observables as well as for flavor and CP violating effective four-fermion operators. We have compared the resulting lower bounds on the Kaluza-Klein (KK) scale in the RS model and a recently proposed model with a metric modified towards the IR brane, which is consistent with oblique parameters without the need for a custodial symmetry. We have randomly generated 40,000 sets of O(1) 5D Yukawa couplings and made a fit of the quark masses an…
We construct the effective theory of the universal Kaehler modulus in warped compactifications using the Hamiltonian formulation of general relativity. The spacetime dependent 10d solution is constructed at the linear level for both the volume modulus and its axionic partner, and nontrivial cancellations of warping effects are found in the dimensional reduction. Our main result is that the Kaehler potential is not corrected by warping, up to an overall shift in the background value of the volume modulus. We extend the analysis beyond the linearized approximation by computing the fully backreac…
We recently proposed a spontaneous A$_{4}$ flavor symmetry breaking scheme implemented in a warped extra dimensional setup to explain the observed pattern of quark and lepton masses and mixings. The main features of this choice are the explanation of fermion mass hierarchies by wave function overlaps, the emergence of tribimaximal (TBM) neutrino mixing and zero quark mixing at the leading order and the absence of tree-level gauge mediated flavor violation. Quark mixing and deviations from TBM neutrino mixing are induced by the presence of bulk A$_4$ flavons, which allow for "cross-brane" inter…
In the context of a warped extra-dimension with Standard Model fields in the bulk, we obtain the general flavor structure of the Higgs couplings to fermions. These couplings will be generically misaligned with respect to the fermion mass matrix, producing large and potentially dangerous flavor changing neutral currents (FCNC's). As recently pointed out in [arXiv:0906.1542], a similar effect is expected from the point of view of a composite Higgs sector, which corresponds to a 4D theory dual to the 5D setup by the AdS-CFT correspondence. We also point out that the effect is independent of the g…
In this thesis, the phenomenology of the Randall-Sundrum setup is investigated. In this context models with and without an enlarged SU(2)_L x SU(2)_R x U(1)_X x P_{LR} gauge symmetry, which removes corrections to the T parameter and to the Z b_L \bar b_L coupling, are compared with each other. The Kaluza-Klein decomposition is formulated within the mass basis, which allows for a clear understanding of various model-specific features. A complete discussion of tree-level flavor-changing effects is presented. Exact expressions for five dimensional propagators are derived, including Yukawa interac…
We study a warped extra-dimension scenario where the Standard Model fields lie in the bulk, with the addition of a fourth family of fermions. We concentrate on the flavor structure of the Higgs couplings with fermions in the flavor anarchy ansatz. Even without a fourth family, these couplings will be generically misaligned with respect to the SM fermion mass matrices. The presence of the fourth family typically enhances the misalignment effects and we show that one should expect them to be highly non-symmetrical in the ${(34)}$ inter-generational mixing. The radiative corrections from the new …
The LHC seems to have made a monumental discovery, Higgs-like particle of mass around 125 GeV with properties akin to a Standard Model Higgs. In the context of a warped theory of flavor, which is theoretically very attractive, this suggests Kaluza-Klein particle masses are likely to be above 10 TeV except possibly for a radion. The interpretation of the SM-like Higgs from the perspective of other interesting beyond the SM scenarios is also likely that the relevant scale is higher than accessible to the LHC. In light of these developments, deeper understanding of flavor and other fundamental is…
Some anomalies in the processes $b\to s\ell\ell$ ($\ell=μ,e$) and $b\to c \ell\barν_\ell$ ($\ell=τ,μ,e$), in particular in the observables $R_K$ and $R_{D^{(\ast)}}$, have been found by the BaBar, LHCb and Belle Collaborations, leading to a possible lepton flavor universality violation. If these anomalies were confirmed they would inevitably lead to physics beyond the Standard Model. In this paper we try to accommodate the present anomalies in an extra dimensional theory, solving the naturalness problem of the Standard Model by means of a warped metric with a strong conformality violation near…
We propose new mechanisms for ameliorating the constraints on the Kaluza-Klein (KK) mass scale from charged lepton flavor violation in the framework of the Standard Model (SM) fields propagating in a warped extra dimension, especially in models accounting for neutrino data. These mechanisms utilize the extended five-dimensional (5D) electroweak gauge symmetry [SU(2)_L x SU(2)_R x U(1)_X] which is already strongly motivated in order to satisfy electroweak precision tests in this framework. New choices of representations for leptons under this symmetry (naturally) can allow small mixing angles f…
In the context of a warped extra-dimension with Standard Model fields in the bulk, we obtain the general flavor structure of the couplings to fermions of both the Higgs scalar and the radion graviscalar. In the Flavor Anarchy paradigm, these couplings are generically misaligned with respect to the fermion mass matrix and moreover the off-diagonal couplings can be estimated parametrically as a function of fermion masses and the observed mixing angles. One can then study the flavor constraints and predictions arising from these couplings.
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 mass…
Within warped extra dimension models that explain flavor through geometry, flavor changing neutral current constraints generally force the Kaluza-Klein scale to be above many TeV. This creates tension with a natural electroweak scale. On the other hand, a much lower scale compatible with precision electroweak and flavor changing neutral current constraints is allowed if we decouple the Kaluza-Klein states of Standard Model gauge bosons from light fermions $c_{\rm light}\simeq c_b\simeq 0.5$ bulk mass parameters). The main signature for this approach is four top quark production via the Kaluza-…
The warped bulk standard model has been studied in the Randall-Sundrum background on $S^1/\Z\times\Z'$ interval with the bulk gauge symmetry $SU(3)\times SU(2)_L\times SU(2)_R\times U(1)_{B-L}$. With the assumption of no large cancellation between the fermion flavor mixing matrices, we present a simple analytic method to determine the bulk masses of standard model fermions in the almost universal bulk Yukawa coupling model. We also predict $U_{e3}$ element of MNS matrix to be near the experimental upper bound when the neutrino masses are of Dirac type.
We study a simple two Higgs doublet model (2HDM) in the Randall-Sundrum scenario, with an IR brane localized Higgs field and a second doublet arising from a $t\bar{t}$ condensate due to strong Kaluza-Klein gluon effects. The effective 2HDM predicts that the ratio of the brane to condensate vacuum expectation values $\tan β\sim 3$. It also predicts a standard model like Higgs boson of mass ${\mathcal{O}}(100)$ GeV and a heavier scalar at the scale of the lowest KK gluon mass, which we take to be $M_{KK} \gtrsim 1.5$ TeV. The pseudoscalar and the charged scalars are degenerate in mass at tree-le…
Recently the LHCb collaboration reported evidence for direct CP violation in charm decays. The value is sufficiently large that either substantially enhanced Standard Model contributions or non-Standard Model physics is required to explain it. In the latter case only a limited number of possibilities would be consistent with other existing flavor-changing constraints. We show that warped extra dimensional models that explain the quark spectrum through flavor anarchy can naturally give rise to contributions of the size required to explain the the LHCb result. The D meson asymmetry arises throug…
We study the production and decay of Kaluza-Klein (KK) gravitons at the Large Hadron Collider (LHC), in the framework of a warped extra dimension in which the Standard Model (SM) fields propagate. Such a scenario can provide solutions to both the Planck-weak hierarchy problem and the flavor puzzle of the SM. In this scenario, the production via $q \bar{q}$ annihilation and decays to the conventional photon and lepton channels are highly suppressed. However, we show that graviton production via gluon fusion followed by decay to longitudinal $Z/W$ can be significant; vector boson fusion is found…
We study the flavor structure of 5D warped models that provide a dual description of a composite pseudo-Goldstone Higgs. We first carefully re-examine the flavor constraints on the mass scale of new physics in the standard Randall-Sundrum-type scenarios, and find that the KK gluon mass should generically be heavier than about 21 TeV. We then compare the flavor structure of the composite Higgs models to those in the RS model. We find new contributions to flavor violation, which while still are suppressed by the RS-GIM mechanism, will enhance the amplitudes of flavor violations. In particular, t…
We present an analysis of the loop-induced magnetic dipole operator in the Randall-Sundrum model of a warped extra dimension with anarchic bulk fermions and an IR brane localized Higgs. These operators are finite at one-loop order and we explicitly calculate the branching ratio for mu to e gamma using the mixed position/momentum space formalism. The particular bound on the anarchic Yukawa and KK scales can depend on the flavor structure of the anarchic matrices. It is possible for a generic model to either be ruled out or unaffected by these bounds without any fine tuning. We quantify how thes…
The framework of a warped extra dimension with the Standard Model (SM) fields propagating in it is a very well-motivated extension of the SM since it can address both the Planck-weak and flavor hierarchy problems of the SM. We consider signals at the 14 and 33 TeV large hadron collider (LHC) resulting from the direct production of the new particles in this framework, i.e.,Kaluza-Klein (KK) excitations of the SM particles. We focus on spin-1 (gauge boson) and spin-2 (graviton) KK particles and their decays to top/bottom quarks (flavor-conserving) and W/Z and Higgs bosons, in particular. We prop…
Amongst the diverse propositions for extra dimensional scenarios, the model of Randall and Sundrum (RS), which offers a solution for the long standing puzzle of the gauge hierarchy problem, has attracted considerable attention from both the theoretical and experimental points of view. In the context of the RS model with gauge bosons and fermions living in the bulk, a novel type of mechanism has arisen for interpreting the strong mass hierarchy of the Standard Model fermions. This purely geometrical mechanism is based on a type and flavor dependent localization of fermions along a warped extra …
In the context of warped extra-dimensional models which address both the Planck-weak- and flavor-hierarchies of the Standard Model (SM), it has been argued that certain observables can be calculated within the 5D effective field theory only with the Higgs field propagating in the bulk of the extra dimension, just like other SM fields. The related studies also suggested an interesting form of decoupling of the heavy Kaluza-Klein (KK) fermion states in the warped 5D SM in the limit where the profile of the SM Higgs approaches the IR brane. We demonstrate that a similar phenomenon occurs when we …
So-called 4321 gauge models at the TeV scale with hierarchical couplings reminiscent of the Standard Model Yukawas offer a coherent combined explanation of the recent $B$-meson anomalies. In these proceedings, based on arXiv:2203.01952, we discuss how such models could arise from a multi-scale theory of flavor, based on a warped fifth dimension with three branes. This higher dimensional construction provides a natural description of flavor hierarchies, addresses the electroweak hierarchy problem, and allows for the Higgs to be identified as a pseudo-Nambu-Goldstone boson emerging from the same…
$B$-anomalies may suggest New Physics at the TeV scale breaking flavor universality. In particular, 4321 gauge models can successfully explain them in a consistent way. In this talk we explore how to UV complete the 4321 model in a 5D warped background to solve simultaneously the Higgs hierarchy problem too, finding interesting connections with the flavor puzzle. We present a model that addresses the $B$-anomalies, flavor hierarchies, and the Higgs hierarchy problem, where quarks and leptons are unified à la Pati-Salam in a non-universal way, and the Higgs appears as a pseudo-Nambu-Goldstone b…
