Search for $s$-Channel Single-Top-Quark Production in Events with Missing Energy Plus Jets in $p\overline{p}$ Collisions at $\sqrt{s}=1.96\mathrm{TeV}$

The first search for single-top-quark production from the exchange of an $s$-channel virtual $W$ boson using events with an imbalance in the total transverse energy, $b$-tagged jets, and no identified leptons is presented. Assuming the electroweak production of top quarks of mass $172.5\mathrm{GeV}/{\mathit{c}}^2$ in the $s$ channel, a cross section of $1.12_{-0.57}^{+0.61}$ ($\text{stat}+\text{syst}$) pb with a significance of 1.9 standard deviations is measured. This measurement is combined with the result obtained from events with an imbalance in total transverse momentum, $b$-tagged jets, and exactly one identified lepton, yielding a cross section of $1.36_{-0.32}^{+0.37}$ ($\text{stat}+\text{syst}$) pb, with a significance of 4.2 standard deviations.

Figure 1

Feynman diagrams for electroweak single-top-quark production: (a) leading-order $t$ channel, (b) next-to-leading-order $t$ channel, and (c) leading-order $s$ channel.

Figure 2

Predicted and observed final discriminant distributions in the signal region for (a) $1T$ two-jet, (b) $1T$ three-jet, (c) $TL$ two-jet, (d) $TL$ three-jet, (e) $TT$ two-jet, and (f) $TT$ three-jet event subsamples.