Searching fortt¯resonances at the CERN Large Hadron Collider

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, $t\overline{t}$ 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 $t\overline{t}\ensuremath{\rightarrow}{\ensuremath{\ell}}^{\ifmmode\pm\else\textpm\fi{}}\ensuremath{\nu}b\overline{b}q{\overline{q}}^{\ensuremath{'}}$ ($\ensuremath{\ell}=e$, $\ensuremath{\mu}$) 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 at large $t\overline{t}$ invariant masses, and include the background originating from $\text{ }\text{ }\mathrm{Wb}\overline{b}+\mathrm{\text{jets}}$, $(Wb+W\overline{b})+\mathrm{\text{jets}}$, $W+\mathrm{\text{jets}}$, and $\mathrm{\text{single top}}+\mathrm{\text{jets}}$ production. We derive semirealistic $5\ensuremath{\sigma}$ 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.