The background tot-quark signals from higher-order QCD contributions

In $p\overline{p}$ collider experiments, the higher-order QCD subprocesses $q\overline{q}\to \mathrm{gQ}\overline{Q}$, $\mathrm{qg}\to \mathrm{qQ}\overline{Q}$, $\mathrm{gg}\to \mathrm{gQ}\overline{Q}$ (with $Q=c,b$) can lead to events with high-$p_T$ leptons and apparently broad jets that may fake the usual signals of $t$-quark production and decay. We evaluate these contributions quantitatively, with plausible approximations, and conclude that the background they provide can be largely eliminated by suitable experimental selection criteria.