Distinguishing a pseudoscalar from a vector $t\bar t$ resonance with top-quark spin correlations at the HL-LHC
Top-quark spin correlations provide a direct probe of the quantum numbers of a resonance decaying to $t\bar t$. We compare a CP-odd type-II two-Higgs-doublet-model pseudoscalar $A$ with a spin-1 leptophobic topcolor $Z'$ in the dilepton channel. The two hypotheses differ in the parton-level helicity correlation by $\De...