Search for pair production of the heavy vectorlike top partner in same-sign dilepton signature at the HL-LHC

TL;DR

This study explores the potential to discover or exclude heavy vectorlike top partners at the HL-LHC through same-sign dilepton signatures, focusing on production via a t-channel process and analyzing the sensitivity in various coupling scenarios.

Contribution

It provides the first detailed analysis of pair production of vectorlike top partners via t-channel at the HL-LHC, including cross section calculations and sensitivity projections in specific coupling models.

Findings

Exclusion limits up to 2σ at HL-LHC for certain parameter regions.

Discovery potential at 5σ for specific coupling strengths.

Constraints on the coupling parameter g* in first-generation quark interactions.

Abstract

New vectorlike quarks are predicted in many new physics scenarios beyond the Standard Model~(SM) and could potentially be discovered at the LHC. Based on a simplified model including a singlet vectorlike top partner with charge $2/3$, we investigate the process $pp \to TT$ via a $t$-channel induced by the couplings between the top partner with the first-generation SM quarks. We calculate the production cross section and further study the observability of the heavy top partner in the channel $T\to Wq$ at the high-luminosity LHC (HL-LHC) using final states with same-sign dileptons (electrons or muons), two jets, and missing transverse momentum. At the 14 TeV LHC with an integrated luminosity of 3000 fb$^{-1}$, the $2\sigma$ exclusion limits, as well as the $5\sigma$ discovery reach in the parameter plane of the two variables $g^{\ast}-R_L$, are respectively obtained at the HL-LHC. We also obtain the $2\sigma$ exclusion limit on the coupling strength parameter $g^{\ast}$ in the case in which the vectorlike top partner is coupled only to the first-generation quarks.