Search for Narrow tt̅ Resonances in pp̅ Collisions at √ s = 1.8 TeV

A search for narrow resonances that decay into tt pairs has been performed using 130 pb -1 of data in the lepton + jets channel collected by the DO detector in pp collisions at √s=1.8 TeV. There is no significant deviation observed from the standard-model predictions at a top-quark mass of 175 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 tt 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 2 , using a theoretical cross section for a width Γ X =0.012M X .