Search for flavour-changing neutral current top-quark decays $t\to qZ$ in proton-proton collisions at $\sqrt{s}=13$ TeV with the ATLAS detector

Understand

A search for flavour-changing neutral-current processes in top-quark decays is presented.

• Data collected with the ATLAS detector from proton-proton collisions at the Large Hadron Collider at a centre-of-mass energy of $\sqrt{s}=13$ TeV, corresponding to an integrated luminosity of 36.1 fb$^{-1}$, are analysed.
• The search is performed using top-quark pair events, with one top quark decaying through the $t\rightarrow qZ$ $(q = u, c)$ flavour-changing neutral-current channel, and the other through the dominant Standard Model mode $t\rightarrow bW$.
• Only $Z$ boson decays into charged leptons and leptonic $W$ boson decays are considered as signal.