Observation of top-quark pair production in association with a photon and measurement of the $t\bar{t}\gamma$ production cross section in pp collisions at $\sqrt{s}=7$ TeV using the ATLAS detector - INSPIRE

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Observation of top-quark pair production in association with a photon and measurement of the $t\bar{t}\gamma$ production cross section in pp collisions at $\sqrt{s}=7$ TeV using the ATLAS detector

ATLAS

Collaboration

Feb 2, 2015

28 pages

Published in:

Phys.Rev.D 91 (2015) 7, 072007

Published: Apr 28, 2015

e-Print:

1502.00586 [hep-ex]

DOI:

10.1103/PhysRevD.91.072007

Report number:

CERN-PH-EP-2014-284

Experiments:

CERN-LHC-ATLAS

View in:

reference search103 citations

Citations per year

Abstract: (APS)

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 data set 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 σtt¯γfid×BR=63±8(stat)-13+17(syst)±1(lumi) fb 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.

Note:

16 pages plus author list + cover pages (29 pages total), 7 figures, 4 tables, submitted to PRD, All figures including auxiliary figures are available at https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/TOPQ-2012-07/

14.65.Ha
12.60.Jv
13.85.Qk
14.80.Ly
p p: colliding beams
top: pair production
photon: associated production
p p: scattering
transverse momentum: missing-energy
higher-order: 1

References(71)

Figures(10)

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