Measurement of the W boson polarisation in tt¯ events from pp collisions at s√ = 8 TeV in the lepton+jets channel with ATLAS

This paper presents a measurement of the polarisation of W bosons from t t  ̄ decays, recon-structed in events with one high-p T lepton and at least four jets. Data from pp collisions√at the LHC were collected at s = 8 TeV and correspond to an integrated luminosity of20.2 fb −1 . The angle θ ∗ betwe...

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Detalhes bibliográficos
Autores: Aaboud, M., Aad, G., Abbott, B., Abdallah, J., Abdinov, O., Alconada Verzini, María Josefina, Alonso, Francisco, Arduh, Francisco Anuar, Dova, Maria Teresa, Hoya, Joaquín, Monticelli, Fernando Gabriel, Wahlberg, Hernan Pablo, Bossio Sola, Jonathan David, Otero y Garzon, Gustavo Javier, Piegaia, Ricardo Nestor, Sacerdoti, Sabrina, Zhukov, K., Zibell. A., Zieminska, D., Zimine, N. I., Zimmermann, C., Zimmermann, S., Zinonos, Z., Zinser, M., Ziolkowski, M., Živković, L., Zobernig, G., Zoccoli, A., Nedden, M. zur, Zurzolo, G., Zwalinski, L., The ATLAS Collaboration
Tipo de documento: artigo
Estado:Versão publicada
Data de publicação:2016
País:Argentina
Recursos:Consejo Nacional de Investigaciones Científicas y Técnicas
Repositório:CONICET Digital (CONICET)
Idioma:inglês
OAI Identifier:oai:ri.conicet.gov.ar:11336/113813
Acesso em linha:http://hdl.handle.net/11336/113813
Access Level:Acceso aberto
Palavra-chave:W Boson
Top
Polarisation
ATLAS
https://purl.org/becyt/ford/1.3
https://purl.org/becyt/ford/1
Descrição
Resumo:This paper presents a measurement of the polarisation of W bosons from t t  ̄ decays, recon-structed in events with one high-p T lepton and at least four jets. Data from pp collisions√at the LHC were collected at s = 8 TeV and correspond to an integrated luminosity of20.2 fb −1 . The angle θ ∗ between the b-quark from the top quark decay and a direct W bo-son decay product in the W boson rest frame is sensitive to the W boson polarisation. Twodifferent W decay products are used as polarisation analysers: the charged lepton and thedown-type quark for the leptonically and hadronically decaying W boson, respectively. Themost precise measurement of the W boson polarisation via the distribution of cos θ ∗ is ob-tained using the leptonic analyser and events in which at least two of the jets are tagged asb-quark jets. The fitted fractions of longitudinal, left- and right-handed polarisation states areF 0 = 0.709 ± 0.019, F L = 0.299 ± 0.015 and F R = −0.008 ± 0.014, and are the mostprecisely measured W boson polarisation fractions to date. Limits on anomalous couplingsof the Wtb vertex are set.

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