In a supersymmetric large extra dimension scenario, the production of Kaluza-Klein gravitinos accompanied by a photino at $e^{+}{e}^{-}$ colliders is studied. We assume that a bulk supersymmetry is softly broken on our brane such that the low-energy theory resembles the MSSM. Low energy supersymmetry breaking is further assumed as in GMSB, leading to a sub-eV mass shift in each KK mode of the gravitino from the corresponding graviton KK mode. Since the photino decays within a detector due to the sufficiently large inclusive decay rate of $\tilde{\gamma }\to \gamma \tilde{G},$ the process $e^{+}{e}^{-}\to \tilde{\gamma }\tilde{G}$ yields single photon events with missing energy. Even if the total cross section can be substantial at $\sqrt{s}=500\mathrm{}\mathrm{GeV},$ the KK graviton background of $e^{+}{e}^{-}\to \gamma G$ is kinematically advantageous and thus much larger. It is shown that the observable $\Delta {\sigma }_{\mathrm{LR}}\equiv \sigma {(e}_L^{-}{e}_R^{+}\left)-\sigma {(e}_R^{-}{e}_L^{+}\right)$ can completely eliminate the KK graviton background but retain most of the KK gravitino signal, which provides a unique and robust method to probe the supersymmetric bulk.

• Received 6 June 2002

DOI:https://doi.org/10.1103/PhysRevD.66.056004