Search for heavy, long-lived neutralinos that decay to photons at CDF II using photon timing

We present the results of the first hadron collider search for heavy, long-lived neutralinos that decay via χ₁⁰→γG in gauge-mediated supersymmetry breaking models. Using an integrated luminosity of 570±34 pb^-1 of pp̄ collisions at √s=1.96 TeV, we select γ+jet+missing transverse energy candidate events based on the arrival time of a high-energy photon at the electromagnetic calorimeter as measured with a timing system that was recently installed on the CDF II detector. We find 2 events, consistent with the background estimate of 1.3±0.7 events. While our search strategy does not rely on model-specific dynamics, we set cross section limits and place the world-best 95% C.L. lower limit on the χ₁⁰ mass of 101 GeV/c² at τ_χ₁⁰=5 ns.