Searching for vector-like leptons decaying into an electron and missing transverse energy in e${}^{+}$e${}^{-}$ collisions with $\sqrt{s}=240$ GeV at the FCC-ee

This analysis delves into the lepton portal dark matter by utilizing Monte Carlo simulated samples from electron-positron collisions at the Future Circular Collider (FCC-ee), operating at a center of mass energy of 240 GeV and an integrated luminosity of 10.8 ab${}^{-1}$. The study explores a specific benchmark scenario in which dark matter is represented as a scalar particle produced as a byproduct of a vector-like lepton. The key signal signature features missing transverse energy alongside dilepton events. Should new physics not be detected, this study establishes 95% confidence level exclusion limits on the mass of the vector-like leptons and the Yukawa coupling.