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 (cid:101) χ 01 → γ (cid:101) G in gauge-mediated supersymmetry breaking models. Using an integrated luminosity of 570 ± 34 pb − 1 of p ¯ p 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 (cid:101) χ 01 mass of 101 GeV /c 2 at τ (cid:101) χ 01 = 5 ns. where each entry reflects a different combination of the electron E T , jet E T and E/ T event requirements. There are slight shifts as the these requirements vary. While the mean of the distribution is close to zero, the systematic variation on the mean of the primary Gaussian of the prompt time distribution is conservatively taken to be 0.2 ns in the background estimates.