Search for charged Higgs bosons through vector-like top quark pair production at the LHC

Abstract

We investigate the discovery prospects for a vector-like top partner (VLT) in the Type-II Two-Higgs-Doublet Model (2HDM-II) extended by a vector-like quark doublet ($TB$) at the 14~TeV LHC. The study focuses on the pair production process $pp\to T\bar{T}\to b{H}^{+}\bar{b}{H}^{-}\to b(tb)\bar{b}(\bar{t}b)$, yielding fully hadronic final states characterized by high $b$-jet multiplicity. Two analysis strategies are employed, requiring at least four or five $b$-tagged jets (4$b$ and 5$b$), to exploit the signal topology. Assuming a charged Higgs mass of $m_{H^{\pm }}\sim 600$~GeV and a systematic uncertainty of $\delta =5\%$, the 4$b$ channel enables discovery up to $m_T\sim 1200$~GeV at $\mathcal{L}=300{\text{fb}}^{-1}$, while the 5$b$ analysis extends the reach to $m_T\sim 1300$~GeV. At higher luminosities of 1000--3000~fb${}^{-1}$, the 5$b$ strategy achieves discovery sensitivity up to $m_T\sim 1400$~GeV. The reach is significantly reduced as $m_{H^{\pm }}$ increases, due to the suppression of the $\text{BR}(T\to H^{+}b)$: for $m_{H^{\pm }}\sim 1000$~GeV, discovery becomes unattainable across all luminosity and systematic uncertainty configurations. Sensitivity is also strongly impacted by systematic uncertainties: for $\delta =10\%$ and $m_{H^{\pm }}<1000$~GeV, discovery remains viable up to $m_T\sim 1200$~GeV in the 5$b$ analysis, while for $\delta =20\%$, no discovery is achievable for $m_T\ge 1000$~GeV.

Comments: 13 pages, 6 figures. Matches published version in PRD