Search for S-Channel Single Top-Quark Production in Proton-Proton Collisions at √s = 8 TeV with the ATLAS Detector
Khalek, S. Abdel
Izen, Joseph M.
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This Letter presents a search at the LHC for s-channel single top-quark production in proton-proton collisions at a centre-of-mass energy of 8 TeV. The analyzed data set was recorded by the ATLAS detector and corresponds to an integrated luminosity of 20.3 fb⁻¹. Selected events contain one charged lepton, large missing transverse momentum and exactly two b-tagged jets. A multivariate event classifier based on boosted decision trees is developed to discriminate s-channel single top-quark events from the main background contributions. The signal extraction is based on a binned maximum-likelihood fit of the output classifier distribution. The analysis leads to an upper limit on the s-channel single top-quark production cross-section of 14.6 pb at the 95% confidence level. The fit gives a cross-section of σ(s) = 5.0 ± 4.3 pb, consistent with the Standard Model expectation.