Supersymmetric Photonic Signals at the CERNe+e−Collider LEP in Light Gravitino Models

We explore and contrast the single-photon and diphoton signals expected at the CERN $e^{+}{e}^{-}$ collider LEP 2 that arise from neutralino-gravitino ( $e^{+}{e}^{-}\to \chi \tilde{G}\to \gamma {+E}_{\mathrm{miss}}$) and neutralino-neutralino ( $e^{+}{e}^{-}\to \chi \chi \to \gamma \gamma {+E}_{\mathrm{miss}}$) production in supersymmetric models with a light gravitino. LEP 1 limits imply that one may observe either one, but not both, of these signals at LEP 2, depending on the values of the neutralino and gravitino masses: single photons for $m_{\chi }\gtrsim M_Z$ and $m_{\tilde{G}}\lesssim 3\times {10}^{-5\mathrm{}}\mathrm{eV}$; diphotons for $m_{\chi }\lesssim M_Z$ and all allowed values of $m_{\tilde{G}}$.