Search for the top quark in<i>pp¯</i>collisions at √<i>s</i>=1.8 TeV

We have searched for evidence of top quark production in pp\ifmmode\bar\else\textasciimacron\fi{} collisions at \ensuremath{\surd}s =1.8 TeV using the D0 detector at the Fermilab Tevatron collider. For an integrated luminosity of 15 ${\mathrm{pb}}^{\mathrm{\ensuremath{-}}1}$, we report results of a search for tt\ifmmode\bar\else\textasciimacron\fi{} pairs in the decay modes tt\ifmmode\bar\else\textasciimacron\fi{}\ensuremath{\rightarrow}e\ensuremath{\mu}+jets,ee+jets,e+jets, and \ensuremath{\mu}+jets. From analyses of these modes we obtain a lower limit on the top quark mass of 131 GeV/${\mathit{c}}^{2}$ at the 95% confidence level, assuming standard model branching fractions and a predicted cross section for tt\ifmmode\bar\else\textasciimacron\fi{} production. We discuss the properties of an event for which expected backgrounds are small.