Comprehensive measurements of $t$-channel single top-quark production cross sections at $\sqrt{s}=7$ TeV with the ATLAS detector

Abstract

This article presents measurements of the $t$-channel single top-quark ($t$) and top-antiquark ($\bar{t}$) total production cross sections $\sigma (tq)$ and $\sigma (\bar{t}q)$, their ratio $R_t=\sigma (tq)/\sigma (\bar{t}q)$, and a measurement of the inclusive production cross section $\sigma (tq+\bar{t}q)$ in proton--proton collisions at $\sqrt{s}=7$ TeV at the LHC. Differential cross sections for the $tq$ and $\bar{t}q$ processes are measured as a function of the transverse momentum and the absolute value of the rapidity of $t$ and $\bar{t}$, respectively. The analyzed data set was recorded with the ATLAS detector and corresponds to an integrated luminosity of 4.59 fb${}^{-1}$. Selected events contain one charged lepton, large missing transverse momentum, and two or three jets. The cross sections are measured by performing a binned maximum-likelihood fit to the output distributions of neural networks. The resulting measurements are $\sigma (tq)=46\pm 6\mathrm{pb}$, $\sigma (\bar{t}q)=23\pm 4\mathrm{pb}$, $R_t=2.04\pm 0.18$, and $\sigma (tq+\bar{t}q)=68\pm 8\mathrm{pb}$, consistent with the Standard Model expectation. The uncertainty on the measured cross sections is dominated by systematic uncertainties, while the uncertainty on $R_t$ is mainly statistical. Using the ratio of $\sigma (tq+\bar{t}q)$ to its theoretical prediction, and assuming that the top-quark-related CKM matrix elements obey the relation $|V_{tb}|\gg |V_{ts}|,|V_{td}|$, we determine $|V_{tb}|=1.02\pm 0.07$.

37 pages plus author list + cover pages (50 pages total), 18 figures, 16 tables, submitted to PRD, All figures including auxiliary figures are available at http://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/TOPQ-2012-21/

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