A mechanism for Kaluza–Klein number violation in UED and implications for LHC

Abstract

We extend our previous analysis on a model where the Higgs does not propagate into an otherwise universal extra dimension. Previously, we computed the cross section for the pair production of Kaluza–Klein excitations of the top quark based on mixing in the Yukawa interactions between the zero-mode top quark and its lowest-lying Kaluza–Klein excitations. In this work, we show that there is also violation of tree-level Kaluza–Klein number conservation in the gauge sector. This allows Kaluza–Klein excitations of the fermions to be produced singly, and opens up new decay channels in the gauge sector. Here, we compute the cross section for the production of the lowest-lying Kaluza–Klein excitations of the top and bottom quarks in the non-universal Higgs model at the Large Hadron Collider, and consider their subsequent decays, including effects from mixing in the gauge sector. The effect is quite large: for example, the pair production of Kaluza–Klein excitations of the bottom quark leads to a pair of top quarks plus a pair of charged weak gauge bosons. Since the production is via the strong interaction, such final states stand out well against the Standard Model background, and are observable at the LHC for a wide range of compactification scales.