Search for Narrowtt¯Resonances inpp¯Collisions ats=1.8TeV

A search for narrow resonances that decay into $t\overline{t}$ pairs has been performed using $130{\mathrm{pb}}^{-1}$ of data in the lepton $+$ jets channel collected by the DØ detector in $p\overline{p}$ collisions at $\sqrt{s}=1.8\mathrm{TeV}$. There is no significant deviation observed from the standard-model predictions at a top-quark mass of $175\mathrm{GeV}/c^2$. We therefore present upper limits at the 95% confidence level on the product of the production cross section and branching fraction to $t\overline{t}$ for narrow resonances as a function of the resonance mass $M_X$. These limits are used to exclude the existence of a leptophobic top-color particle with mass $M_X<560\mathrm{GeV}/c^2$, using a theoretical cross section for a width ${\Gamma }_X=0.012M_X$.