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Copious production of top-antitop quark pairs at hadron colliders has enabledvarious probes into the properties and interactions of top quarks. Among thevarious presently measured observables, the forward-backward asymmetry (FBA) int tbar production measured at the Tevatron significantly deviates from thestandard model predictions, and many models of new physics have been inventedto explain the puzzle. We consider the consistency of the simplifiedsingle-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 tbarproduction measurements. Among the considered models only an axigluon canreproduce all Tevatron observables, without being in severe tension with therecent LHC results on t tbar production cross section, charge asymmetry andtop-spin correlations. The LHC charge asymmetry measurements exclude the W' andZ' explanations of the Tevatron FBA anomaly. On the other hand, all scalarmodels predict notable deviations in several top spin observables, and therecent top spin correlation measurement using the "helicity" spin quantizationaxis by ATLAS already provides a significant constraint on possibleexplanations of the Tevatron FBA anomaly. Future precise measurements of topspin correlations and especially top polarization could differentiate betweenscalar t(u)-channel models, while they are less sensitive to pure axigluoncontributions.

Discerning New Physics in Top-Antitop Production using Top Spin Observables at Hadron Colliders