Observation of top-quark pair production in association with a photon and measurement of the t¯tγ production cross section in pp collisions at sqrt(s) = 7 TeV using the ATLAS detector

A search is performed for top-quark pairs (tt¯) produced together with a photon (γ) with transverse energy greater than 20 GeV using a sample of tt¯ candidate events in final states with jets, missing transverse momentum, and one isolated electron or muon. The dataset used corresponds to an integrat...

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Detalles Bibliográficos
Autores: Aad, G., Abbott, B., Abdallah, J., Abdinov, O., Aben, R., Alconada Verzini, María Josefina, Alonso, Francisco, Arduh, Francisco Anuar, Dova, Maria Teresa, Monticelli, Fernando Gabriel, Wahlberg, Hernan Pablo, Otero y Garzon, Gustavo Javier, Piegaia, Ricardo Nestor, Reisin, Hernan Diego, Sacerdoti, Sabrina, Zimmermann, C., Zimmermann, R., 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 recurso: artículo
Estado:Versión publicada
Fecha de publicación:2015
País:Argentina
Institución:Consejo Nacional de Investigaciones Científicas y Técnicas
Repositorio:CONICET Digital (CONICET)
Idioma:inglés
OAI Identifier:oai:ri.conicet.gov.ar:11336/53609
Acceso en línea:http://hdl.handle.net/11336/53609
Access Level:acceso abierto
Palabra clave:ATLAS
TOP
Photons
https://purl.org/becyt/ford/1.3
https://purl.org/becyt/ford/1
Descripción
Sumario:A search is performed for top-quark pairs (tt¯) produced together with a photon (γ) with transverse energy greater than 20 GeV using a sample of tt¯ candidate events in final states with jets, missing transverse momentum, and one isolated electron or muon. The dataset used corresponds to an integrated luminosity of 4.59 fb−1 of proton-proton collisions at a center-of-mass energy of 7 TeV recorded by the ATLAS detector at the CERN Large Hadron Collider. In total 140 and 222 tt¯γ candidate events are observed in the electron and muon channels, to be compared to the expectation of 79±26 and 120±39 non-tt¯γ background events respectively. The production of tt¯γ events is observed with a significance of 5.3 standard deviations away from the null hypothesis. The tt¯γ production cross section times the branching ratio (BR) of the single-lepton decay channel is measured in a fiducial kinematic region within the ATLAS acceptance. The measured value is σfidtt¯γ=63±8(stat.)+17−13(syst.)±1(lumi.) per lepton flavor, in good agreement with the leading-order theoretical calculation normalized to the next-to-leading-order theoretical prediction of 48±10 fb.

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