Search for electroweak production of single top quarks inpp¯collisions

We present a search for electroweak production of single top quarks in the $\mathrm{e}\mathrm{l}\mathrm{e}\mathrm{c}\mathrm{t}\mathrm{r}\mathrm{o}\mathrm{n}+\mathrm{j}\mathrm{e}\mathrm{t}\mathrm{s}$ and $\mathrm{m}\mathrm{u}\mathrm{o}\mathrm{n}+\mathrm{j}\mathrm{e}\mathrm{t}\mathrm{s}$ decay channels. The measurements use $\approx 90{\mathrm{pb}}^{-1}$ of data from Run 1 of the Fermilab Tevatron collider, collected at 1.8 TeV with the DØ detector between 1992 and 1995. We use events that include a tagging muon, implying the presence of a b jet, to set an upper limit at the $95\%$ confidence level on the cross section for the s-channel process $p\overline{p}\to tb+X$ of 39 pb. The upper limit for the t-channel process $p\overline{p}\to tqb+X$ is 58 pb.