Study on the prospects of a $t\bar{t}$ resonance search in events with one lepton at a High Luminosity LHC

A study on the prospects of a search for a new particle decaying to a top quark pair at the High Luminosity LHC using Monte Carlo simulations is presented. The proposed search will assume an integrated luminosity of 3000 fb$^{-1}$ of proton-proton collision data taken at $\sqrt{s}$ = 14 TeV. Detector effects are accounted for using parameterised estimates of the performance of an upgraded ATLAS detector. The search is carried out by examining the $t\bar{t}$ invariant mass spectrum for localised excesses or deficits. A statistical analysis sets expected upper limits on the cross section of a $t\bar{t}$ resonance in a benchmark model for several signal masses. The mass reach of a search for a Z' boson in the TopColour model at the HL-LHC is estimated to be 4 TeV. This is an increase of $\sim$ 1 TeV relative to the estimated limit using 300 fb$^{−1}$ that is expected from the LHC prior to the upgrade.