Searching for t-bar t Resonances at the Large Hadron Collider

TL;DR

This paper evaluates the Large Hadron Collider's potential to discover and distinguish Kaluza-Klein gluon resonances in top quark pair production, considering realistic detector effects and background processes.

Contribution

It provides a detailed analysis of the LHC's discovery reach for KK gluons in bulk Randall-Sundrum models, including background modeling and model differentiation capabilities.

Findings

KK gluons up to 4 TeV can be discovered at the LHC.

Discrimination between different KK gluon models is highly model dependent.

The study incorporates realistic detector effects and background processes.

Abstract

Many new physics models predict resonances with masses in the TeV range which decay into a pair of top quarks. With its large cross section, t-bar t production at the Large Hadron Collider (LHC) offers an excellent opportunity to search for such particles. We present a detailed study of the discovery potential of the CERN Large Hadron Collider for Kaluza-Klein (KK) excitations of the gluon in bulk Randall-Sundrum (RS) models in the t-bar t -> ell^+/- nu b-bar bq-bar q' (ell=e, mu) final state. We utilize final states with one or two tagged b-quarks, and two, three or four jets (including b-jets). Our calculations take into account the finite resolution of detectors, the energy loss due to b-quark decays, the expected reduced b-tagging efficiency at large t-bar t invariant masses, and include the background originating from Wb-bar b+jets, (Wb+W-bar b)+jets, W+jets, and single top + jets production. We derive semi-realistic 5 sigma discovery limits for nine different KK gluon scenarios, and compare them with those for KK gravitons, and a Z_H boson in the Littlest Higgs model. We also analyze the capabilities of the LHC experiments to differentiate between individual KK gluon models and measure the couplings of KK gluons to quarks. We find that, for the parameters and models chosen, KK gluons with masses up to about 4 TeV can be discovered at the LHC. The ability of the LHC to discriminate between different bulk RS models, and to measure the couplings of the KK gluons is found to be highly model dependent.