TY  - JOUR
AU  - ATLAS Collaboration (Aad, G. et al
AU  - Cabrera Urban, S.
AU  - Castillo Gimenez, V.
AU  - Costa, M. J.
AU  - Ferrer, A.
AU  - Fiorini, L.
AU  - Fuster, J.
AU  - Garcia, C.
AU  - Garcia Navarro, J. E.
AU  - Gonzalez de la Hoz, S.
AU  - Hernandez Jimenez, Y.
AU  - Higon-Rodriguez, E.
AU  - Irles Quiles, A.
AU  - Kaci, M.
AU  - King, M.
AU  - Lacasta, C.
AU  - Lacuesta, V. R.
AU  - Marti-Garcia, S.
AU  - Mitsou, V. A.
AU  - Moles-Valls, R.
AU  - Oliver Garcia, E.
AU  - Pedraza Lopez, S.
AU  - Perez Garcia-Estañ, M. T.
AU  - Romero Adam, E.
AU  - Ros, E.
AU  - Salt, J.
AU  - Sanchez Martinez, V.
AU  - Soldevila, U.
AU  - Sanchez, J.
AU  - Torro Pastor, E.
AU  - Valero, A.
AU  - Valladolid Gallego, E.
AU  - Valls Ferrer, J. A.
AU  - Vos, M.
PY  - 2015
DA  - 2015//
TI  - Observation of top-quark pair production in association with a photon and measurement of the t(t)over-bar gamma production cross section in pp collisions at root s=7 TeV using the ATLAS detector
T2  - Phys. Rev. D
JO  - Physical Review D
SP  - 072007
EP  - 28pp
VL  - 91
IS  - 7
PB  - Amer Physical Soc
AB  - A search is performed for top-quark pairs (t (t) over bar) produced together with a photon (gamma) with transverse energy greater than 20 GeV using a sample of t (t) over bar 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 t (t) over bar gamma candidate events are observed in the electron and muon channels, to be compared to the expectation of 79 +/- 26 and 120 +/- 39 non-t (t) over bar gamma background events, respectively. The production of t (t) over bar gamma events is observed with a significance of 5.3 standard deviations away from the null hypothesis. The t (t) over bar gamma 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 sigma(fid)(t (t) over bar gamma) x 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.
SN  - 1550-7998
UR  - http://arxiv.org/abs/1502.00586
UR  - https://doi.org/10.1103/PhysRevD.91.072007
DO  - 10.1103/PhysRevD.91.072007
LA  - English
N1  - WOS:000353545500001
ID  - ATLASCollaborationAad_etal2015
ER  -