Khachatryan, V.Sirunyan, A. M.Tumasyan, A.Adam, W.Asilar, E.Bergauer, T.The CMS Collaboration2025-03-072025-03-0720161029-8479https://doi.org/10.1007/JHEP04(2016)073https://hdl.handle.net/20.500.12507/2992A first measurement of the top quark spin asymmetry, sensitive to the top quark polarisation, in t-channel single top quark production is presented. It is based on a sample of pp collisions at a centre-of-mass energy of 8TeV corresponding to an integrated luminosity of 19.7 fb(-1). A high-purity sample of t-channel single top quark events with an isolated muon is selected. Signal and background components are estimated using a fit to data. A differential cross section measurement, corrected for detector effects, of an angular observable sensitive to the top quark polarisation is performed. The differential distribution is used to extract a top quark spin asymmetry of 0.26 +/- 0.03(stat) +/- 0.10(syst), which is compatible with a p-value of 4.6% with the standard model prediction of 0.44.eninfo:eu-repo/semantics/openAccessHadron-Hadron scattering (experiments)Top physicsArticle4WOS:0003743397000012-s2.0-8496389381910.1007/JHEP04(2016)073Q1Q1