Implications of effective axial-vector coupling of gluon for $t\bar{t}$ spin polarizations at the LHC

TL;DR

This paper investigates how an effective axial-vector gluon coupling influences top-antitop spin polarization observables at the LHC, highlighting the potential to confirm or refute the Tevatron top asymmetry anomaly and set bounds on new physics scale.

Contribution

It introduces a leading-order QCD analysis of axial-vector gluon coupling effects on top pair spin observables, emphasizing invariant mass dependent asymmetries and their sensitivity to new physics scale.

Findings

High invariant mass asymmetries are more sensitive to the new physics scale.

LHC can potentially confirm or exclude the Tevatron top asymmetry anomaly.

Lower bounds on the new physics scale can be established if no deviations are observed.

Abstract

We analyze the impact of effective axial-vector coupling of the gluon on spin polarization observables in $t\bar{t}$ pair production at the LHC. Working at leading order in QCD, we compute the $t\bar{t}$ spin-correlation and left-right spin asymmetry coefficients in the helicity basis in the laboratory frame as functions of the new physics scale $\Lambda$ associated with this coupling. We found that the $t\bar{t}$ invariant mass dependent asymmetries are more sensitive to the scale $\Lambda$ than the corresponding inclusive ones, in particular when suitable cuts selecting high $t\bar{t}$ invariant mass regions are imposed. In the context of this scenario, we show that the LHC has potential either to confirm or to rule out the Tevatron FB top asymmetry anomaly by analyzing the $t\bar{t}$ spin-correlation and left-right polarization asymmetries. On the other hand, stringent lower bound on the new physics scale $\Lambda$ can be set in this scenario if no significant deviations from the SM predictions for those observables will be measured.