Searching for the vector-like X-quark at the future electron–proton colliders

Abstract

Abstract In a simplified model including an exotic vector-like X-quark (VLQ-X) with electric charge 5/3, we investigate the process $$e^{+}p \rightarrow \bar{\nu }_{e}X+\bar{\nu }_{e}X\bar{t}$$ e + p → ν ¯ e X + ν ¯ e X t ¯ induced by the couplings between the VLQ-X and the first- and third-generation quarks at the future ep colliders. We further explore the prospects of discovering the VLQ-X via the $$X\rightarrow tW$$ X → t W decay model at the electron–hadron Future Circular Collider (FCC-eh) with its proposed 60 GeV electron beam and 50 TeV proton beam. We focus our analysis on the final states, including two same-sign lepton (electrons or muons) or $$\mu \mu $$ μ μ pairs, at least one b-tagged jet, and large missing transverse momentum. By performing a detailed signal-to-background analysis and detector simulations, the 95% confidence level exclusion limits and $$5\sigma $$ 5 σ discovery reaches are presented in terms of parameter space regions.