Probing Universal Extra Dimension at the International Linear Collider

In the context of an universal extra-dimensional scenario, we consider production of the first Kaluza-Klein electron positron pair in an $e^+e^-$ collider as a case-study for the future International Linear Collider. The Kaluza-Klein electron decays into a nearly degenerate Kaluza-Klein photon and a standard electron, the former carrying away missing energy. The Kaluza-Klein electron and photon states are heavy with their masses around the inverse radius of compactification, and their splitting is controlled by radiative corrections originating from bulk and brane-localised interactions. We look for the signal event $e^+e^- +$ large missing energy for $\sqrt s = 1$ TeV and observe that with a few hundred fb$^{-1}$ luminosity the signal will be hard to miss since standard model backgrounds remain well within control. We also comment on how this signal can be distinguished from similar events from supersymmetry.