  The sensitivity of top quark pair production at the Large Hadron Collider to
the presence and nature of an underlying Z' boson is studied, accounting for
six-fermion decay with full tree-level Standard Model ttbar interference and
all intermediate particles allowed off-shell. Focus is placed on the
lepton-plus-jets final state, emulating experimental conditions, including
kinematic requirements and top quark pair reconstruction in the presence of
missing transverse energy and combinatorial ambiguity in jet-top assignment.
Considering a resonance with mass of 4 TeV, and assuming 300 inverse fb of
proton-proton collisions with a centre of mass energy of 13 TeV data, a
combination of forward-backward and top polarisation asymmetries are shown to
distinguish Z' embedded by different classes of Grand-Unified-Theory-inspired
models. In combination with the differential cross section, they may be used to
increase the significance of the signal when tested against the Standard Model,
as shown using a likelihood-based statistical test.
