Top quark search with the D0 1992–1993 data sample

We present results on the search for the top quark in pp¯ collisions at √s =1.8 TeV with an integrated luminosity of 13.5±1.6 ${\mathrm{pb}}^{\mathrm{-}1}$. We have considered tt¯ production in the standard model using electron and muon dilepton decay channels (tt¯→eμ+jets, ee+jets, and μμ+jets) and single-lepton decay channels (tt¯→e+jets and μ+jets) with and without tagging of b quark jets. An analysis of these data optimized for top quark masses below 140 GeV/${\mathit{c}}^2$ gives a lower top quark mass limit of 128 GeV/${\mathit{c}}^2$. An analysis optimized for higher top quark masses yields 9 events with an expected background of 3.8±0.9. If we assume that the excess is due to tt¯ production, and assuming a top quark mass of 180 GeV/${\mathit{c}}^2$, we obtain a cross section of 8.2±5.1 pb.