Kaluza-Klein excitations of gauge bosons at the LHC

We consider the Randall-Sundrum extra-dimensional model with fields propagating in the bulk based on an extended electroweak gauge symmetry with specific fermion charges and localizations that allow to explain the LEP anomaly of the forward-backward asymmetry for b-quarks, AFBb. We study the manifestations of the strongly-interacting and electroweak gauge boson Kaluza-Klein excitations VKK at the LHC, with masses of the order of a few TeV, which dominantly decays into top and bottom quark pairs. We first analyze the two-body tree-level production processes pp→tt¯ and bb¯ in which the Kaluza-Klein (KK) excitations of gauge bosons are exchanged. We find that the additional channels can lead to a significant excess of events with respect to the Standard Model prediction; characteristic top quark polarization and angular asymmetries are quantitatively studied where the polarization is the probe the chiral structure of couplings to excited states. We then analyze higher order production processes for the gauge boson excitations which have too weak or no couplings to light quarks and, in particular, the loop induced process gg→VKK→tt¯ and bb¯ in which the anomalous ggVKK four-dimensional vertex has to be regulated. The RS effects in this process, as well as in the four-body reactions pp→tt¯bb¯, tt¯tt¯, bb¯bb¯ and in the related three-body reactions gb→btt¯, bbb¯, in which the VKK excitations are mainly radiated off the heavy quarks, are shown to be potentially difficult to test at LHC, due to small phase space and low parton density for MKK≳3TeV.