Comprehensive measurements oft-channel single top-quark production cross sections ats=7  TeVwith the ATLAS detector

Abstract

This article presents measurements of the t-channel single top-quark (t) and top-antiquark (t) total production cross sections σðtqÞ and σðtqÞ, their ratio R t ¼ σðtqÞ=σðtqÞ, and a measurement of the inclusive production cross section σðtq þtqÞ in proton-proton collisions at ffiffi ffi s p ¼ 7 TeV at the LHC. Differential cross sections for the tq andtq processes are measured as a function of the transverse momentum and the absolute value of the rapidity of t andt, 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 σðtqÞ ¼ 46 AE 1ðstatÞ AE 6ðsystÞ pb, σðtqÞ ¼ 23 AE 1ðstatÞ AE 3ðsystÞ pb, R t ¼ 2.04 AE 0.13ðstatÞ AE 0.12ðsystÞ, and σðtq þtqÞ ¼ 68 AE 2ðstatÞ AE 8ðsystÞ 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 σðtq þtqÞ to its theoretical prediction, and assuming that the top-quark-related CKM matrix elements obey the relation jV tb j ≫ jV ts j; jV td j, we determine jV tb j ¼ 1.02 AE 0.07.

Top-Quark Physics at the LHC

“…The extraction is independent of assumptions about the number of quark generations and about the unitarity of Measurement |V tb | 2 |V tb | limit at 95% CL t-ch., ATLAS [167] 1.02 ± 0.07 > 0.88 t-ch., CMS [166] 0.998 ± 0.038(exp) ± 0.016(theo) > 0.92 tW -ch., ATLAS [168] 1.03…”

“…Additional requirements on kinematic observables, such as the missing transverse momentum or the transverse mass of the W boson, are imposed in order to further remove background. Detailed and precise results are available from ATLAS and CMS [163][164][165][166][167].…”

“…The largeness of the LHC data samples and of the t-channel single top cross section give access to detailed studies of differential distributions [167] and properties, such as the top-quark polarisation, W helicity distributions, and mass measurements. At the time of preparation of this volume, the publication of the latter measurements is still in progress.…”

Probing the W tb vertex structure in t-channel single-top-quark production and decay in pp collisions at s = 8 $$ \sqrt{s}=8 $$ TeV with the ATLAS detector

“…The likelihood function [60] is given by the product of Poisson probability terms associated with the fitted regions, combined with the product of Gaussian priors to constrain -13 -JHEP04 (2017) . The observed distributions are compared to the predicted signal and background distributions, normalised to the results of the maximum-likelihood fit.…”

Top physics at the LHC

“…Besides interesting in its own right, the t-channel process is a background to many new physics processes involving both neutral and charged Higgs production. Based on samples of 4.6 fb −1 by ATLAS and 1.14 fb −1 by CMS of the run at 7 TeV, the t-channel cross section is [174,175] ATLAS : σ t = 68 ± 2 (stat) ± 8 (sys) pb , CMS : σ t = 67.2 ± 3.7 (stat) ± 4.8 (sys) pb . Figure 3: Doubly resonant diagrams in NLO corrections to W t production.…”