  The LHC discovery potential of heavy top partners decaying into a top quark
and a $Z$ boson is studied in the trilepton channel at $\sqrt{s}=13$ TeV. The
clean multilepton final state allows to strongly reduce the background
contaminations and to reconstruct the $T'$ mass. We show that a simple
cut-and-count analysis probes the parameter space of a simplified model as
efficiently as a dedicated multivariate analysis. The trilepton signature
finally turns out to be as sensitive in the low $T'$ mass region as the
complementary channel with a fully hadronic top quark, and more sensitive in
the large mass domain. The reinterpretation in terms of the top-$Z$-up
anomalous coupling is shown.
