Search for flavour-changing neutral current top-quark decays to qZqZ in pppp collision data collected with the ATLAS detector at s√=8s√=8 TeV

Abstract

Ajuts: 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 MINECO, Spain and EPLANET, ERC, ERDF, FP7, Horizon 2020 and Marie Skłodowska-Curie Actions, European Union. Funded by SCOAP3. ; A search for the flavour-changing neutral-current decay is presented. Data collected by the ATLAS detector during 2012 from proton-proton collisions at the Large Hadron Collider at a centre-of-mass energy of TeV, corresponding to an integrated luminosity of 20.3 fb, are analysed. Top-quark pair-production events with one top quark decaying through the () channel and the other through the dominant Standard Model mode are considered as signal. Only the decays of the Z boson to charged leptons and leptonic W boson decays are used. No evidence for a signal is found and an observed (expected) upper limit on the branching ratio of () is set at the 95 % confidence level