Search for Pair Production of Supersymmetric Top Quarks in Dilepton Events from p anti-p Collisions at s**(1/2) =1.96 TeV

We present the results of a search for pair production of the supersymmetric partner of the top quark (the stop quark t-bar_1) decaying to a b-quark and a chargino chi-bar+/-_1 with a subsequent chi-bar+/-_1 decay into a neutralino chi-bar0_1, lepton ell, and neutrino nu. Using a data sample corresponding to 2.7 fb-1 of integrated luminosity of p anti-p collisions at s**(1/2) = 1.96 TeV collected by the CDF II detector, we reconstruct the mass of candidate stop events and fit the observed mass spectrum to a combination of standard model processes and stop quark signal. We find no evidence for t-bar_1 t-bar_1 production and set 95% C.L. limits on the masses of the stop quark and the neutralino for several values of the chargino mass and the branching ratio B(chi-bar+/-_1 --> chi-bar0_1 ell+/- nu_).