Search for Pair Production of Supersymmetric Top Quarks in Dilepton Events from pp¯ Collisions at s=1.96TeV

We present the results of a search for pair production of the supersymmetric partner of the top quark (the top squark t∼₁) decaying to a b quark and a chargino χ∼₁^± with a subsequent χ∼₁^± decay into a neutralino χ∼₁⁰, lepton ℓ, and neutrino ν. Using a data sample corresponding to 2.7fb^-1 of integrated luminosity of pp¯ collisions at s=1.96TeV collected by the CDF II detector, we reconstruct the mass of top squark candidate events and fit the observed mass spectrum to a combination of standard model processes and t∼₁t∼¯₁ signal. We find no evidence for t∼₁t∼¯₁ production and set 95% C.L. limits on the masses of the top squark and the neutralino for several values of the chargino mass and the branching ratio B(χ∼₁^±→χ∼₁⁰ℓ^±ν).