CERN LHC signals for warped electroweak neutral gauge bosons

Abstract

We study signals at the Large Hadron Collider (LHC) for Kaluza-Klein (KK) excitations of the electroweak gauge bosons in the framework with the standard model (SM) gauge and fermion fields propagating in a warped extra dimension. Such a framework addresses both the Planck-weak and flavor hierarchy problems of the SM. Unlike the often studied ${Z}^{\ensuremath{'}}$ cases, in this framework, there are three neutral gauge bosons due to the underlying $SU(2{)}_{L}\ifmmode\times\else\texttimes\fi{}SU(2{)}_{R}\ifmmode\times\else\texttimes\fi{}U(1{)}_{X}$ gauge group in the bulk. Furthermore, couplings of these KK states to light quarks and leptons are suppressed, whereas those to top and bottom quarks are enhanced compared to the SM gauge couplings. Therefore, the production of light quark and lepton states is suppressed relative to other beyond the SM constructions, and the fermionic decays of these states are dominated by the top and bottom quarks, which are, though, overwhelmed by KK gluons dominantly decaying into them. However, as we emphasize in this paper, decays of these states to longitudinal $W$, $Z$ and Higgs are also enhanced similarly to the case of top and bottom quarks. We show that the $W$, $Z$ and Higgs final states can give significant sensitivity at the LHC to $\ensuremath{\sim}2(3)\text{ }\text{ }\mathrm{TeV}$ KK scale with an integrated luminosity of $\ensuremath{\sim}100\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$ ($\ensuremath{\sim}1\text{ }\text{ }{\mathrm{ab}}^{\ensuremath{-}1}$). Since current theoretical framework(s) favor KK masses $\ensuremath{\gtrsim}3\text{ }\text{ }\mathrm{TeV}$, a luminosity upgrade of LHC is likely to be crucial in observing these states.