# Measurement of the production cross-section of a single top quark in association with a W boson at 8 TeV with the ATLAS experiment

 Title: Measurement of the production cross-section of a single top quark in association with a W boson at 8 TeV with the ATLAS experiment Author: Franklin, Melissa; Huth, John; Ippolito, Valerio; Lazovich, Tomo; Lopez Mateos, David; Mercurio, Kevin ; Morii, Masahiro; Spearman, William; Sun, Siyuan; Tolley, Emma; Tuna, Alexander; Yen, Andy; Zambito, Stefano Note: Order does not necessarily reflect citation order of authors. Citation: ATLAS Collaboration. 2016. “Measurement of the Production Cross-Section of a Single Top Quark in Association with a W Boson at 8 TeV with the ATLAS Experiment.” Journal of High Energy Physics 2016 (1) (January). doi:10.1007/jhep01(2016)064. Full Text & Related Files: 1510.03752.pdf (1.292Mb; PDF) Abstract: The cross-section for the production of a single top quark in association with a W boson in proton--proton collisions at s√=8 TeV is measured. The dataset corresponds to an integrated luminosity of 20.3 fb−1, collected by the ATLAS detector in 2012 at the Large Hadron Collider at CERN. Events containing two leptons and one central b-jet are selected. The Wt signal is separated from the backgrounds using boosted decision trees, each of which combines a number of discriminating variables into one classifier. Production of Wt events is observed with a significance of 7.7σ. The cross-section is extracted in a profile likelihood fit to the classifier output distributions. The Wt cross-section, inclusive of decay modes, is measured to be 23.0±1.3(stat.)+3.2−3.5(syst.)±1.1(lumi.) pb. The measured cross-section is used to extract a value for the CKM matrix element |Vtb| of 1.01±0.10 and a lower limit of 0.80 at the 95\% confidence level. The cross-section for the production of a top quark and a W boson is also measured in a fiducial acceptance requiring two leptons with pT>25 GeV and |η|<2.5, one jet with pT>20 GeV and |η|<2.5, and EmissT>20 GeV, including both Wt and top-quark pair events as signal. The measured value of the fiducial cross-section is 0.85±0.01(stat.)+0.06−0.07(syst.)±0.03(lumi.) pb. Published Version: doi:10.1007/JHEP01(2016)064 Terms of Use: This article is made available under the terms and conditions applicable to Open Access Policy Articles, as set forth at http://nrs.harvard.edu/urn-3:HUL.InstRepos:dash.current.terms-of-use#OAP Citable link to this page: http://nrs.harvard.edu/urn-3:HUL.InstRepos:34487700 Downloads of this work: