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.

Figure 1

Representative Feynman diagrams of single-top-quark production. (a) and (b) are $t$-channel processes, and (c) is the $s$-channel process.

Figure 2

Discriminant distribution for all channels combined of the (a) LF analysis, (b) ME analysis, (c) NN analysis and (d) combined superdiscriminant analysis. Points with error bars indicate the data. The predicted signal and background distributions are shown as stacked histograms. The insets show the candidate events in the signal regions. A summary of all results is shown in (e).