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 $|V_{tb}|=1.02 \pm 0.07$.
Highlights
In proton-proton collisions at the LHC, top quarks are produced at unprecedented rates, allowing studies that were intractable before
In this article we present measurements of σðtq þtqÞ, σðtqÞ, mass σðtqÞ, energy and of tpheffiffi s cross-section ratio Rt 1⁄4 7 TeV, using the at a full center-ofdata set corresponding to an integrated luminosity of 4.59 fb−1
The analysis described in this article uses pp collision data collected at a center-of-mass energy of 7 TeV with the ATLAS detector [20] at the LHC between March and November 2011
Summary
In proton-proton (pp) collisions at the LHC, top quarks are produced at unprecedented rates, allowing studies that were intractable before. A measurement of the combined top-quark and top-antiquark cross section σðtq þtqÞ 1⁄4 σðtqÞ þ σðtqÞ is well suited to constrain Vtb. 112006-1 or the b-quark PDF. In this article we present measurements of σðtq þtqÞ, σðtqÞ, mass σðtqÞ, energy and of tpheffiffi s cross-section ratio Rt 1⁄4 7 TeV, using the at a full center-ofdata set corresponding to an integrated luminosity of 4.59 fb−1. In pp collisions at s 1⁄4 7 TeV, the total inclusive cross sections of top-quark and top-antiquark production in the t channel are predicted to be σðtqÞ 1⁄4 41.9þ−01..98 pb; σðtqÞ 1⁄4 22.7þ−10..09 pb; and σðtq þtqÞ 1⁄4 64.6þ−22..07 pb; with approximate next-to-next-to-leading-order (NNLO) precision [9], assuming a top-quark mass of mt 1⁄4 172.5 GeV and using the MSTW2008 NNLO [10] PDF set.
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