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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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: Artículo
Estado:Published version
Fecha de publicación:2016
País:Argentina
Institución:Consejo Nacional de Investigaciones Científicas y Técnicas
Repositorio:CONICET Digital (CONICET)
Lenguaje:Inglés
OAI Identifier:oai:ri.conicet.gov.ar:11336/113813
Acceso en línea:http://hdl.handle.net/11336/113813
Nivel de acceso:Acceso abierto
Palabra clave:W Boson
Top
Polarisation
ATLAS
https://purl.org/becyt/ford/1.3
https://purl.org/becyt/ford/1
Sumario: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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