Clark, Brian LeeFranklin, MelissaHuth, JohnIppolito, ValerioLazovich, TomoLopez Mateos, DavidMercurio, KevinMorii, MasahiroSpearman, WilliamSun, SiyuanTolley, EmmaTuna, AlexanderYen, AndyZambito, Stefano2017-06-202016ATLAS Collaboration. 2016. “Evidence for single top-quark production in the s-channel in proton-proton collisions at s√=8 TeV with the ATLAS detector using the Matrix Element Method.” Physics Letters B 756 (May): 228–246. doi:10.1016/j.physletb.2016.03.017.0370-2693http://nrs.harvard.edu/urn-3:HUL.InstRepos:33058572This Letter presents evidence for single top-quark production in the s-channel using proton-proton collisions at a centre-of-mass energy of 8 TeV with the ATLAS detector at the CERN Large Hadron Collider. The analysis is performed on events containing one isolated electron or muon, large missing transverse momentum and exactly two b-tagged jets in the final state. The analysed data set corresponds to an integrated luminosity of 20.3 fb−1. The signal is extracted using a maximum-likelihood fit of a discriminant which is based on the matrix element method and optimized in order to separate single-top-quark s-channel events from the main background contributions, which are top-quark pair production and W boson production in association with heavy-flavour jets. The measurement leads to an observed signal significance of 3.2 standard deviations and a measured cross-section of σs=4.8±0.8(stat.)+1.6−1.3(syst.) pb, which is consistent with the Standard Model expectation. The expected significance for the analysis is 3.9 standard deviations.en-USJournal Article2017-06-2010.1016/j.physletb.2016.03.017