Search for new heavy quarks in electron-muon events at the Fermilab Tevatron Collider

Abstract

A search for tt\ifmmode\bar\else\textasciimacron\fi{}\ensuremath{\rightarrow}e\ensuremath{\mu}+X in pp\ifmmode\bar\else\textasciimacron\fi{} collisions at s\ensuremath{\surd}\ifmmode\bar\else\textasciimacron\fi{} TeV is described. The production and decay of top-quark--antiquark pairs is considered in the context of the standard model. The analysis is based on data with an integrated luminosity of 4.4 ${\mathrm{pb}}^{\mathrm{\ensuremath{-}}1}$ recorded with the Collider Detector at Fermilab. An upper limit on the tt\ifmmode\bar\else\textasciimacron\fi{} cross section is obtained, and the top quark in the mass range 28--72 GeV/${c}^{2}$ is excluded at the 95% C.L. The same limits apply to a possible fourth-generation, charge -(1/3, b' quark, decaying via the charged current.