Search for flavour-changing neutral currents in processes with one top quark and a photon using 81 fb−1
of pp collisions at s=13TeV with the ATLAS experiment
A search for flavour-changing neutral current (FCNC) events via the coupling of a top quark, a photon, and an up or charm quark is presented using 81 fb−1 of proton–proton collision data taken at a centre-of-mass energy of 13 TeV with the ATLAS detector at the LHC. Events with a photon, an electron or muon, a b-tagged jet, and missing transverse momentum are selected. A neural network based on kinematic variables differentiates between events from signal and background processes. The data are consistent with the background-only hypothesis, and limits are set on the strength of the tqγ coupling in an effective field theory. These are also interpreted as 95% CL upper limits on the cross section for FCNC tγ production via a left-handed (right-handed) tuγ coupling of 36 fb (78 fb) and on the branching ratio for t→γu of 2.8×10−5 (6.1×10−5). In addition, they are interpreted as 95% CL upper limits on the cross section for FCNC tγ production via a left-handed (right-handed) tcγ coupling of 40 fb (33 fb) and on the branching ratio for t→γc of 22×10−5 (18×10−5).
Aad, G; Abbott, B; Abbott, DC; Abed Abud, A; Abeling, K; Abhayasinghe, DK; Abidi, SH; Abouzeid, OS; Abraham, NL; Abramowicz, H; Abreu, H; Abulaiti, Y; Acharya, BS; Achkar, B; Adachi, S; Adam, L; Adam Bourdarios, C; Adamczyk, L; Adamek, L; Adelman, J; Adersberger, M; Adiguzel, A; Adorni, S; Adye, T; Affolder, AA; Afik, Y; Agapopoulou, C; Agaras, MN; Aggarwal, A; Agheorghiesei, C; Aguilar-Saavedra, JA; Ahmadov, F; Ahmed, WS; Ai, X; Aielli, G; Akatsuka, S; Åkesson, TPA; Akilli, E; Akimov, AV; Al Khoury, K; Alberghi, GL; Albert, J; Alconada Verzini, MJ; Alderweireldt, S; Aleksa, M; Aleksandrov, IN; Alexa, C; Alexandre, D; Alexopoulos, T; Alfonsi, A; Alfonsi, F; Alhroob, M; Ali, B; Alimonti, G; Alison, J; Alkire, SP; Allaire, C; Allbrooke, BMM; Allen, BW; Allport, PP; Aloisio, A; Alonso, A; Alonso, F; Alpigiani, C; Alshehri, AA; Alvarez Estevez, M; Álvarez Piqueras, D; Alviggi, MG; Amaral Coutinho, Y; Ambler, A; Ambroz, L; Amelung, C; Amidei, D; Amor Dos Santos, SP; Amoroso, S; Amrouche, CS; An, F; Anastopoulos, C; Andari, N; Andeen, T; Anders, CF; Anders, JK; Andreazza, A; Andrei, V; Anelli, CR; Angelidakis, S; Angerami, A; Anisenkov, AV; Annovi, A; Antel, C; Anthony, MT; Antonelli, M; Antrim, DJA; Anulli, F; Aoki, M; Aparisi Pozo, JA; Aperio Bella, L; Arabidze, G; Araque, JP; Araujo Ferraz, V
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