Top quark search with the D0 1992–1993 data sample

We present results on the search for the top quark in pp\ifmmode\bar\else\textasciimacron\fi{} collisions at \ensuremath{\surd}s =1.8 TeV with an integrated luminosity of 13.5\ifmmode\pm\else\textpm\fi{}1.6 ${\mathrm{pb}}^{\mathrm{\ensuremath{-}}1}$. We have considered tt\ifmmode\bar\else\textasciimacron\fi{} production in the standard model using electron and muon dilepton decay channels (tt\ifmmode\bar\else\textasciimacron\fi{}\ensuremath{\rightarrow}e\ensuremath{\mu}+jets, ee+jets, and \ensuremath{\mu}\ensuremath{\mu}+jets) and single-lepton decay channels (tt\ifmmode\bar\else\textasciimacron\fi{}\ensuremath{\rightarrow}e+jets and \ensuremath{\mu}+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\ifmmode\pm\else\textpm\fi{}0.9. If we assume that the excess is due to tt\ifmmode\bar\else\textasciimacron\fi{} production, and assuming a top quark mass of 180 GeV/${\mathit{c}}^{2}$, we obtain a cross section of 8.2\ifmmode\pm\else\textpm\fi{}5.1 pb.

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