Measurement of the Single-Top-Quark Production Cross Section at CDF

We report a measurement of the single-top-quark production cross section in $2.2{\mathrm{fb}}^{-1}$ of $p\overline{p}$ collision data collected by the Collider Detector at Fermilab at $\sqrt{s}=1.96\mathrm{TeV}$. Candidate events are classified as signal-like by three parallel analyses which use likelihood, matrix element, and neural network discriminants. These results are combined in order to improve the sensitivity. We observe a signal consistent with the standard model prediction, but inconsistent with the background-only model by 3.7 standard deviations with a median expected sensitivity of 4.9 standard deviations. We measure a cross section of ${2.2}_{-0.6}^{+0.7}(\mathrm{stat}+\mathrm{syst})\mathrm{pb}$, extract the Cabibbo-Kobayashi-Maskawa matrix-element value $|V_{tb}|={0.88}_{-0.12}^{+0.13}(\mathrm{stat}+\mathrm{syst})\pm 0.07(\mathrm{theory})$, and set the limit $|V_{tb}|>0.66$ at the 95% C.L.