KK-number non-conserving decays: Signal of n=2n=2 excitations of extra-dimensional models at the LHC

In the simplest universal extra-dimensional models Kaluza–Klein (KK) parity distinguishes the states with odd and even KK-number. We calculate the coupling of a 2n  -level top quark to a top quark and the Higgs scalar (both n=0n=0 states), absent at the tree level, which is mediated by strong interactions at one-loop. We show that the strength of this coupling is independent of n. We observe that the decay due to this coupling, which conserves KK-parity, can be a few per cent of the phase space suppressed decay to two n-level states which proceeds through tree-level couplings. We explore the prospects of verification of this result at the Large Hadron Collider through the production of a second-level KK top–antitop pair both of which subsequently decay to a zero mode top quark/antiquark and a Higgs boson.