Observation of top-quark pair production in association with a photon and measurement of the tt ¯ γ production cross section in pp collisions at s √ =7 TeV using the ATLAS detector

ATLAS, Collaboration; Beck, Hans Peter; Cervelli, Alberto; Ereditato, Antonio; Haug, Sigve; Kabana, Sonja; Meloni, Federico; Pretzl, Klaus-Peter; Stramaglia, Maria Elena; Stucci, Stefania; Weber, Michael (2015). Observation of top-quark pair production in association with a photon and measurement of the tt ¯ γ production cross section in pp collisions at s √ =7 TeV using the ATLAS detector. Physical review. D - particles, fields, gravitation, and cosmology, D91(7), 072007. American Physical Society 10.1103/PhysRevD.91.072007

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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 σ fid tt ¯ 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.

Item Type:

Journal Article (Original Article)

Division/Institute:

10 Strategic Research Centers > Albert Einstein Center for Fundamental Physics (AEC)
08 Faculty of Science > Physics Institute > Laboratory for High Energy Physics (LHEP)

UniBE Contributor:

Beck, Hans Peter; Cervelli, Alberto; Ereditato, Antonio; Haug, Sigve; Meloni, Federico; Pretzl, Klaus-Peter; Stramaglia, Maria Elena; Stucci, Stefania and Weber, Michael

Subjects:

500 Science > 530 Physics

ISSN:

1550-7998

Publisher:

American Physical Society

Language:

English

Submitter:

Annette Krebs-Wegenast

Date Deposited:

07 Sep 2016 11:29

Last Modified:

11 Sep 2016 02:12

Publisher DOI:

10.1103/PhysRevD.91.072007

ArXiv ID:

1502.00586v2

Additional Information:

Kollaboration - Es sind nur die Berner Autoren namentlich erwähnt

BORIS DOI:

10.7892/boris.87659

URI:

https://boris.unibe.ch/id/eprint/87659

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