Measurement of top quark polarisation in t-channel single top quark production
Austrian Federal Ministry of Science, Research and Economy ; Austrian Science Fund ; Belgian Fonds de la Recherche Scientifique ; Fonds voor Wetenschappelijk Onderzoek ; Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) ; Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) ; Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro (FAPERJ) ; Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) ; Bulgarian Ministry of Education and Science ; CERN ; Chinese Academy of Sciences ; Ministry of Science and Technology ; National Natural Science Foundation of China ; Colombian Funding Agency (COLCIENCIAS) ; Croatian Ministry of Science, Education and Sport ; Croatian Science Foundation ; Research Promotion Foundation, Cyprus ; Ministry of Education and Research, Estonia ; Estonian Research Council, Estonia ; European Regional Development Fund, Estonia ; Academy of Finland ; Finnish Ministry of Education and Culture ; Helsinki Institute of Physics ; Institut National de Physique Nucleaire et de Physique des Particules / CNRS, France ; Commissariat a l'Energie Atomique et aux Energies Alternatives / CEA, France ; Bundesministerium fur Bildung und Forschung, Germany ; Deutsche Forschungsgemeinschaft, Germany ; Helmholtz-Gemeinschaft Deutscher Forschungszentren, Germany ; General Secretariat for Research and Technology, Greece ; National Scientific Research Foundation, Hungary ; National Innovation Office, Hungary ; Department of Atomic Energy, India ; Department of Science and Technology, India ; Institute for Studies in Theoretical Physics and Mathematics, Iran ; Science Foundation, Ireland ; Istituto Nazionale di Fisica Nucleare, Italy ; Ministry of Science, ICT and Future Planning, Republic of Korea ; National Research Foundation (NRF), Republic of Korea ; Lithuanian Academy of Sciences ; Ministry of Education (Malaysia) ; CINVESTAV ; CONACYT ; SEP ; UASLP-FAI ; Ministry of Business, Innovation and Employment, New Zealand ; Pakistan Atomic Energy Commission ; Ministry of Science and Higher Education, Poland ; National Science Centre, Poland ; Fundacao para a Ciencia e a Tecnologia, Portugal ; JINR, Dubna ; Ministry of Education and Science of the Russian Federation ; Federal Agency of Atomic Energy of the Russian Federation ; Russian Academy of Sciences ; Russian Foundation for Basic Research ; Ministry of Education, Science and Technological Development of Serbia ; Secretaria de Estado de Investigacion, Desarrollo e Innovacion, Spain ; Programa Consolider-Ingenio, Spain ; ETH Board ; ETH Zurich ; PSI ; SNF ; UniZH ; Canton Zurich ; SER ; Ministry of Science and Technology, Taipei ; Thailand Center of Excellence in Physics ; Institute for the Promotion of Teaching Science and Technology of Thailand ; Special Task Force for Activating Research ; National Science and Technology Development Agency of Thailand ; Scientific and Technical Research Council of Turkey ; Turkish Atomic Energy Authority ; National Academy of Sciences of Ukraine ; State Fund for Fundamental Researches, Ukraine ; Science and Technology Facilities Council, U.K. ; US Department of Energy ; US National Science Foundation ; Marie-Curie programme (European Union) ; European Research Council (European Union) ; EPLANET (European Union) ; Leventis Foundation ; A. P. Sloan Foundation ; Alexander von Humboldt Foundation ; Belgian Federal Science Policy Office ; Fonds pour la Formation a la Recherche dans l'Industrie et dans l'Agriculture (FRIA-Belgium) ; Agentschap voor Innovatie door Wetenschap en Technologie (IWT-Belgium) ; Ministry of Education, Youth and Sports (MEYS) of the Czech Republic ; Council of Science and Industrial Research, India ; HOMING PLUS programme of the Foundation for Polish Science ; European Union, Regional Development Fund ; OPUS programme of the National Science Center (Poland) ; Compagnia di San Paolo (Torino) ; MIUR (Italy) ; Thalis programme - EU-ESF ; Aristeia programme - EU-ESF ; Greek NSRF ; National Priorities Research Program by Qatar National Research Fund ; Rachadapisek Sompot Fund for Postdoctoral Fellowship, Chulalongkorn University (Thailand) ; Welch Foundation ; University of Malaya (Malaysia) ; Science and Technology Facilities Council ; Estonian Research Council, Estonia: IUT23-4 ; Estonian Research Council, Estonia: IUT23-6 ; MIUR (Italy): 20108T4XTM ; Welch Foundation: C-1845 ; Science and Technology Facilities Council: GRIDPP ; Science and Technology Facilities Council: ST/I000305/1 ; Science and Technology Facilities Council: ST/K001256/1 ; Science and Technology Facilities Council: ST/N000250/1 ; Science and Technology Facilities Council: ST/H000925/1 ; Science and Technology Facilities Council: ST/L005603/1 ; Science and Technology Facilities Council: ST/M004775/1 ; Science and Technology Facilities Council: ST/N000242/1 ; Science and Technology Facilities Council: ST/K001531/1 ; Science and Technology Facilities Council: PP/E002803/1 ; Science and Technology Facilities Council: CMS ; Science and Technology Facilities Council: ST/K003542/1 GRID PP ; Science and Technology Facilities Council: ST/K001639/1 CMS Upgrades ; Science and Technology Facilities Council: ST/K001639/1 ; Science and Technology Facilities Council: ST/I003622/1 ; Science and Technology Facilities Council: ST/J004871/1 ; Science and Technology Facilities Council: ST/H000925/2 ; Science and Technology Facilities Council: ST/J005479/1 ; Science and Technology Facilities Council: ST/K003542/1 ; Science and Technology Facilities Council: ST/N001273/1 ; Science and Technology Facilities Council: ST/M002020/1 ; Science and Technology Facilities Council: ST/K003542/1 GRIDPP ; Science and Technology Facilities Council: ST/K003224/1 CMS Upgrades ; Science and Technology Facilities Council: PP/E000479/1 ; Science and Technology Facilities Council: ST/M004775/1 GRIDPP ; Science and Technology Facilities Council: ST/I003622/1 GRIDPP ; A 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.