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

G Aad; B Abbott; J Abdallah; S Abdel Khalek; O Abdinov; R Aben; B Abi; M Abolins; OS Abouzeid; H Abramowicz; H Abreu; R Abreu; Y Abulaiti; BS Acharya; L Adamczyk; DL Adams; J Adelman; S Adomeit; T Adye; T Agatonovic-Jovin; JA Aguilar-Saavedra; M Agustoni; SP Ahlen; F Ahmadov; G Aielli; H Akerstedt; TPA Åkesson; G Akimoto; AV Akimov; GL Alberghi; J Albert; S Albrand; MJ Alconada Verzini; M Aleksa; IN Aleksandrov; C Alexa; G Alexander; G Alexandre; T Alexopoulos; M Alhroob; G Alimonti; L Alio; J Alison; BMM Allbrooke; LJ Allison; PP Allport; J Almond; A Aloisio; A Alonso; F Alonso; C Alpigiani; A Altheimer; B Alvarez Gonzalez; MG Alviggi; K Amako; Y Amaral Coutinho; C Amelung; D Amidei; SP Amor Dos Santos; A Amorim; S Amoroso; N Amram; G Amundsen; C Anastopoulos; LS Ancu; N Andari; T Andeen; CF Anders; G Anders; KJ Anderson; A Andreazza; V Andrei; XS Anduaga; S Angelidakis; I Angelozzi; P Anger; A Angerami; F Anghinolfi; AV Anisenkov; N Anjos; A Annovi; A Antonaki; M Antonelli; A Antonov; J Antos; F Anulli; M Aoki; L Aperio Bella; R Apolle; G Arabidze; I Aracena; Y Arai; JP Araque; ATH Arce; JF Arguin; S Argyropoulos; M Arik; AJ Armbruster; O Arnaez; V Arnal

Journal article

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

G Aad, B Abbott, J Abdallah, S Abdel Khalek, O Abdinov, R Aben, B Abi, M Abolins, OS Abouzeid, H Abramowicz, H Abreu, R Abreu, Y Abulaiti, BS Acharya, L Adamczyk, DL Adams, J Adelman, S Adomeit, T Adye, T Agatonovic-Jovin Show all

Physical Review D Particles Fields Gravitation and Cosmology | Published : 2015

DOI: 10.1103/PhysRevD.91.072007

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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 signi..

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University of Melbourne Researchers

Federico Scutti Author

Elisabetta Barberio Author

Matteo Volpi Author

G. N. Taylor Author

Grants

Awarded by European Commission

Funding Acknowledgements

We thank CERN for the very successful operation of the LHC, as well as the support staff from our institutions without whom ATLAS could not be operated efficiently. We acknowledge the support of ANPCyT, Argentina; YerPhI, Armenia; ARC, Australia; BMWFW and FWF, Austria; ANAS, Azerbaijan; SSTC, Belarus; CNPq and FAPESP, Brazil; NSERC, NRC and CFI, Canada; CERN; CONICYT, Chile; CAS, MOST and NSFC, China; COLCIENCIAS, Colombia; MSMT CR, MPO CR and VSC CR, Czech Republic; DNRF, DNSRC and Lundbeck Foundation, Denmark; EPLANET, ERC and NSRF, European Union; IN2P3-CNRS, CEA-DSM/IRFU, France; GNSF, Georgia; BMBF, DFG, HGF, MPG and AvH Foundation, Germany; GSRT and NSRF, Greece; RGC, Hong Kong SAR, China; ISF, MINERVA, GIF, I-CORE and Benoziyo Center, Israel; INFN, Italy; MEXT and JSPS, Japan; CNRST, Morocco; FOM and NWO, Netherlands; BRF and RCN, Norway; MNiSW and NCN, Poland; GRICES and FCT, Portugal; MNE/IFA, Romania; MES of Russia and NRC KI, Russian Federation; JINR; MSTD, Serbia; MSSR, Slovakia; ARRS and MIZS, Slovenia; DST/NRF, South Africa; MINECO, Spain; SRC and Wallenberg Foundation, Sweden; SER, SNSF and Cantons of Bern and Geneva, Switzerland; NSC, Taiwan; TAEK, Turkey; STFC, the Royal Society and Leverhulme Trust, United Kingdom; DOE and NSF, United States of America. The crucial computing support from all WLCG partners is acknowledged gratefully, in particular from CERN and the ATLAS Tier-1 facilities at TRIUMF (Canada), NDGF (Denmark, Norway, Sweden), CC-IN2P3 (France), KIT/GridKA (Germany), INFN-CNAF (Italy), NL-T1 (Netherlands), PIC (Spain), ASGC (Taiwan), RAL (UK) and BNL (USA) and in the Tier-2 facilities worldwide.