Search for the Supersymmetric Partner of the Top Quark in Dilepton Events from $p\overline{p}$ Collisions at $\sqrt{s}=1.8\mathrm{T}\mathrm{e}\mathrm{V}$

We have searched for pair production of the supersymmetric partner of the top quark (stop) in $107{\mathrm{p}\mathrm{b}}^{-1}$ of $p\overline{p}$ collisions at $\sqrt{s}=1.8\mathrm{T}\mathrm{e}\mathrm{V}$ collected by the Collider Detector at Fermilab (CDF). Each stop is assumed to decay into a lepton, bottom quark, and supersymmetric neutrino. Such a scenario would give rise to events with two leptons, two hadronic jets, and a substantial imbalance of transverse energy. No evidence of such a stop signal has been found. We exclude stop masses in the region ($80\le m_{\tilde{t}}\le 135\mathrm{G}\mathrm{e}\mathrm{V}/c^2$) in the mass plane of stop versus sneutrino.

Figure 1

Data and expected background after preselection. Tight and second lepton transverse energies, missing transverse energy [for comparison we also show the missing $E_T$ distribution for a 10 times stop signal of $m_{\tilde{t}}(m_{\tilde{\nu }})=100(75)\mathrm{G}\mathrm{e}\mathrm{V}/c^2$], and jet multiplicity shown for events with opposite charge leptons. The last high bins contain overflows.

Figure 2

Stop and sneutrino mass plane showing the CDF $95\%$ C.L. excluded region as hatched area. For the three-body stop decay, $\tilde{t}\to l\tilde{\nu }b$, a $33.3\%$ branching ratio to each of the three lepton flavors is used.