Search for s-channel single top-quark production in proton-proton collisions at s√=8 TeV with the ATLAS detector

• Main Author: Onofre, A.
• Publication Date: 2015
• Other Authors: Castro, Nuno Filipe Silva Fernandes, ATLAS Collaboration
• Format: Article
• Language: eng
• Source: Repositórios Científicos de Acesso Aberto de Portugal (RCAAP)
• Download full: https://hdl.handle.net/1822/39902
• topic: Electroweak interaction; Top physics; Heavy quark production; Experimental results; ATLAS; Top quark; Electroweak production; s-Channel; Ciências Naturais::Ciências Físicas; Science & Technology

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 σs=5.0±4.3 pb, consistent with the Standard Model expectation.