Study of the discovery potential of light custodians in a clean decay channel at the LHC

Abstract

Models of warped extra dimensions with custodial symmetry usually predict the existence of a light Kaluza-Klein fermion arising as a partner of the right-handed top quark, sometimes called light custodians which we will denotebR. The production of these particles at the LHC can give rise to multi-W events which could be observed in same-sign dilepton channels, but its mass reconstruction is challenging. In this letter we study the possibility of finding a signal for the pair production of this new particle at the LHC focusing on a rarer, but cleaner decay mode of a light custodian into a Z boson and a b-quark. In this mode it would be possible to reconstruct the light custodian mass. In addition to the dominant standard model QCD production processes, we include the contribution of a Kaluza-Klein gluon first mode. We find that thebR stands out from the background as a peak in the bZ invariant mass. However, when taking into account only the electronic and muonic decay modes of the Z boson and b−tagging efficiencies, the LHC will have access only to the very light range of masses, mb = O(500) GeV.

Anomalous gauge couplings from composite Higgs and warped extra dimensions

“…6 Some of the resonances we discuss below could be rather light. However, their masses have to be somewhat higher than v as they would already have been detected at the LHC otherwise, see [16][17][18]. We can thus safely assume Λ v and neglect the electroweak mass splittings.…”

New theories for the Fermi scale

“…While my presentation has been focussed on the gauge sector, the fermionic sector of composite Higgs models, in particular in the top sector, provides also very interesting signatures easily accessible at the first stages of the LHC operation [91,95,126,127,128,129,130,131]. In particular the same-sign dilepton final states offer a sensitive probe to the top partners [127,131] with a discovery potential up to 500 GeV (resp.…”

Search strategies for top partners in composite Higgs models

“…Many suggestions for dedicated searches for such top partners have been put forward [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37][38]. Indeed, there are already more on the market than the experiments have the resources to implement, with just a few analyses having appeared thus far.…”