  Copious production of top-antitop quark pairs at hadron colliders has enabled
various probes into the properties and interactions of top quarks. Among the
various presently measured observables, the forward-backward asymmetry (FBA) in
t tbar production measured at the Tevatron significantly deviates from the
standard model predictions, and many models of new physics have been invented
to explain the puzzle. We consider the consistency of the simplified
single-resonance models containing a color octet axial-vector ("axigluon"),
color triplet or sextet weak singlet scalars, weak isodoublet scalar,
flavor-changing neutral Z', or charged W' vector boson with existing t tbar
production measurements. Among the considered models only an axigluon can
reproduce all Tevatron observables, without being in severe tension with the
recent LHC results on t tbar production cross section, charge asymmetry and
top-spin correlations. The LHC charge asymmetry measurements exclude the W' and
Z' explanations of the Tevatron FBA anomaly. On the other hand, all scalar
models predict notable deviations in several top spin observables, and the
recent top spin correlation measurement using the "helicity" spin quantization
axis by ATLAS already provides a significant constraint on possible
explanations of the Tevatron FBA anomaly. Future precise measurements of top
spin correlations and especially top polarization could differentiate between
scalar t(u)-channel models, while they are less sensitive to pure axigluon
contributions.
