Search for Pair Production of Stop Quarks Mimicking Top Event Signatures

We update our search for the pair-produced super-symmetric partner of the top quark (stop quark) from 1.9fb−1 to 2.7fb−1 of data collected with CDF II. We search for the scalar top quarks via their decay channel: t̃1 → b + χ̃1 → b+χ̃1+ν+` which gives an event signature similar to that of a top dilepton event. We reconstruct events under the stop decay hypothesis and use the reconstructed stop mass as a discriminating kinematic variable in the fit to data. We separate this analysis into two channels, events that contain a b-tagg, and events that do not. In the signal region the number of events observed and the kinematic distribution of the reconstructed stop mass is consistent with the SM predictions. Thus no evidence for scalar top quark pair-production is observed. We set 95% C.L. limits on the dilepton branching ratio at theory production cross section, in the three-dimensional space of super-symmetric particle masses, t̃1, χ̃1 , χ̃ 0 1 assuming 100% branching ratio of stop quark decays into bottom quark and chargino.