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.

Aad, G., Abbott, B., Abdallah, J., Abdel Khalek, S., Abdinov, O., Aben, R., et al. (2015). Observation of top-quark pair production in association with a photon and measurement of the t t ¯ γ production cross section in pp collisions at √s =7 TeV using the ATLAS detector. PHYSICAL REVIEW D, PARTICLES, FIELDS, GRAVITATION, AND COSMOLOGY, 91(7), 072007-1-072007-28 [10.1103/PhysRevD.91.072007].

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

ALBERGHI, GIAN LUIGI;BELLAGAMBA, LORENZO;BOSCHERINI, DAVIDE;BRUNI, ALESSIA;BRUNI, GRAZIANO;DE CASTRO, STEFANO;FABBRI, LAURA;FRANCHINI, MATTEO;GABRIELLI, ALESSANDRO;GIACOBBE, BENEDETTO;MENGARELLI, ALBERTO;POLINI, ALESSANDRO;RINALDI, LORENZO;ROMANO, MARINO;SBARRA, CARLA;SEMPRINI CESARI, NICOLA;SPIGHI, ROBERTO;VALENTINETTI, SARA;VILLA, MAURO;Vivarelli, I.;ZOCCOLI, ANTONIO;
2015

Abstract

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.
2015
Aad, G., Abbott, B., Abdallah, J., Abdel Khalek, S., Abdinov, O., Aben, R., et al. (2015). Observation of top-quark pair production in association with a photon and measurement of the t t ¯ γ production cross section in pp collisions at √s =7 TeV using the ATLAS detector. PHYSICAL REVIEW D, PARTICLES, FIELDS, GRAVITATION, AND COSMOLOGY, 91(7), 072007-1-072007-28 [10.1103/PhysRevD.91.072007].
Aad, G.; Abbott, B.; Abdallah, J.; Abdel Khalek, S.; Abdinov, O.; Aben, R.; Abi, B.; Abolins, M.; Abouzeid, O.S.; Abramowicz, H.; Abreu, H.; Abreu, R....espandi
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/548665
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