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

ATLAS Collaboration, G Aad, Torsten Åkesson, Simona Bocchetta, Lene Bryngemark, Eric Edward Corrigan, Caterina Doglioni, Kristian Gregersen, Eva Brottmann Hansen, Vincent Hedberg, Göran Jarlskog, Charles Kalderon, Edgar Kellermann, Balazs Konya, Else Lytken, Katja Mankinen, Caterina Marcon, Ulf Mjörnmark, Geoffrey André Adrien Mullier, Ruth PöttgenTrine Poulsen, Eleni Skorda, Oxana Smirnova, L Zwalinski

Research output: Contribution to journalArticlepeer-review

Abstract

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). © 2019 The Author(s)
Original languageEnglish
Article number135082
JournalPhysics Letters, Section B: Nuclear, Elementary Particle and High-Energy Physics
Volume800
DOIs
Publication statusPublished - 2020

Subject classification (UKÄ)

  • Subatomic Physics

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