Precision Electroweak Data and Unification of Couplings in Warped Extra Dimensions

This is the first of two papers aimed at economically capturing the collider phenomenology of warped extra dimensions with bulk Standard Model fields, where the hierarchy problem is solved non-supersymmetrically. This scenario is related via the AdS/CFT correspondence to that of partial compositeness of the Standard Model. We present a purely four-dimensional, two-sector effective field theory describing the Standard Model fields and just their first Kaluza-Klein/composite ex...

We study production of Kaluza-Klein gluons (KKG) at the Large Hadron Collider (LHC) in the framework of a warped extra dimension with the Standard Model (SM) fields propagating in the bulk. We show that the detection of KK gluon is challenging since its production is suppressed by small couplings to the proton's constituents. Moreover, the KK gluon decays mostly to top pairs due to an enhanced coupling and hence is broad. Nevertheless, we demonstrate that for m_{KKG} \lesssim...

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 v...

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 l...

This work presents a general formalism to analyze a generic bulk scalar field in a multiple warped extra-dimensional model with arbitrary number of extra dimensions. The Kaluza-Klein mass modes along with the self-interaction couplings are determined and the possibility of having lowest lying KK mode masses near TeV scale are discussed. Also some numerical values for low-lying KK modes has been presented showing explicit localization around TeV scale. It is argued that the ap...

We study gauge coupling unification in the presence of extra dimensions compactified at a few TeV. Achieving unification requires a large number of gauge boson Kaluza-Klein excitations lighter than the string scale, such that the higher-dimensional gauge couplings are O(1) in string scale units. Corrections to the gauge couplings from two or more loops are about 10% or larger, hence string (or M) theory is generally expected to be strongly coupled in TeV-scale extra-dimension...

After discussing the localization of Abelian and non-Abelian gauge fields and Higgs fields on a thick brane, we introduce a procedure of dimensional reduction and its consequences to the rescaled parameters of the boson sector of the Standard Model. The parameters encodes some power dependence on the extra dimension, usually narrow, warp factor and hence it also depend on the position related with the extra dimension inside the thick brane. In this vein, the observable parame...

Within a minimal extension of the SM in 4+1 dimensions, we study how Kaluza Klein excitations of the SM gauge bosons affect the electroweak precision observables. Asymmetries in Z decays provide the dominant bound on the compactification scale M of the extra dimension. If the higgs is so light that will be discovered at LEP2, we find the following 95% CL bounds: M > 3.5 TeV (if the higgs lives in the extra dimension) and M > 4.3 TeV (if the higgs is confined to our 4 dimensio...

In models with universal extra dimensions (UED), the lightest Kaluza-Klein excitation of neutral electroweak gauge bosons is a stable, weakly interacting massive particle and thus is a candidate for dark matter thanks to Kaluza-Klein parity. We examine concrete model realizations of such dark matter in the context of non-minimal UED extensions. The boundary localized kinetic terms for the electroweak gauge bosons lead to a non-trivial mixing among the first Kaluza-Klein excit...

We present an analysis of the loop-induced couplings of the Higgs boson to the massless gauge fields (gluons and photons) in the warped extra dimension models where all Standard Model fields propagate in the bulk. We show that in such models corrections to the hgg and $h{\gamma}{\gamma}$ couplings are potentially very large. These corrections can lead to generically sizable deviations in the production and decay rates of the Higgs boson, even when the new physics states lie b...