KK-number non-conserving decays: Signal of n = 2 excitations of Extra-Dimensional Models at the LHC

TL;DR

This paper investigates KK-number non-conserving decays in universal extra-dimension models, calculating loop-induced couplings and exploring their potential detection at the LHC through n=2 KK top pair production and decay.

Contribution

It provides the first calculation of one-loop KK-number non-conserving couplings involving the top quark and Higgs in universal extra dimensions, highlighting their potential experimental signatures.

Findings

Loop-induced KK-number non-conserving couplings are independent of n.

Decay rates due to these couplings can be a few percent of KK-parity conserving decays.

Prospects for detecting n=2 KK top pairs at the LHC are discussed.

Abstract

In the simplest universal extra-dimension 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 = 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 an n = 2 KK top-antitop pair both of which subsequently decay to a zero mode top quark/antiquark and a Higgs boson.