Search for flavour-changing neutral currents in processes with one top quark and a photon using 81 fb¯¹ of pp collisions at √s=13 TeV with the ATLAS experiment

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2020

Authors

Aad, G.
Abbott, B.
Abbott, D.C.
Abed Abud, A.
Abeling, K.
Abhayasinghe, D.K.
Abidi, S.H.
AbouZeid, O.S.
Abraham, N.L.
Abramowicz, H.

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Physics Letters B, 2020; 800:1-21

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G. Aad, B. Abbott, D.C. Abbott, A. Abed Abud ... Paul Jackson ... Abhishek Sharma ... et al. (The Atlas Collaboration)

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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−1of 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 tqγcoupling in an effective field theory. These are also interpreted as 95% CL upper limits on the cross section for FCNC tγproduction via a left-handed (right-handed) tuγcoupling of 36 fb (78 fb) and on the branching ratio for t→γuof 2.8 ×10−5(6.1 ×10−5). In addition, they are interpreted as 95% CL upper limits on the cross section for FCNC tγproduction via a left-handed (right-handed) tcγcoupling of 40 fb (33 fb) and on the branching ratio for t→γcof 22 ×10−5(18 ×10−5).

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© 2019 The Author(s). Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/). Funded by SCOAP³

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