Isosinglet vectorlike leptons at $e^+e^-$ colliders

Abstract: We study weak isosinglet vectorlike leptons that decay through a small mixing with the tau lepton, for which the discovery and exclusion reaches of the Large Hadron Collider and future proposed hadron colliders are limited. We show how an $e^+ e^-$ collider may act as a discovery machine for these $\tau^{\prime}$ particles, demonstrate that the $\tau^{\prime}$ mass peak can be reconstructed in a variety of distinct signal regions, and explain how the $\tau^{\prime}$ branching ratios may be measured.