Top quark forward-backward asymmetry, FCNC decays and like-sign pair production as a joint probe of new physics

TL;DR

This paper investigates how specific new physics models involving a Z' boson can explain the top quark forward-backward asymmetry anomaly and predict correlated signals like FCNC decays and like-sign top pairs at the LHC, offering potential for model discrimination.

Contribution

It analyzes two Z'-based models to explain the A^t_FB anomaly and predicts distinct correlated signatures for experimental testing at the LHC.

Findings

Both models can explain the A^t_FB deviation.

Models predict enhanced like-sign top pair production.

Distinct observable correlations can distinguish models.

Abstract

The anomaly of the top quark forward-backward asymmetry $A^t_{FB}$ observed at the Tevatron can be explained by the t-channel exchange of a neutral gauge boson (Z') which has sizable flavor changing coupling for top and up quarks. This gauge boson can also induce the top quark flavor-changing neutral-current (FCNC) decays and the like-sign top pair production at the LHC. In this work we focus on two models which predict such a Z', namely the left-right model and the U(1)_X model, to investigate the correlated effects on $A^t_{FB}$, the FCNC decays $t -> u V$ ($V=g,Z,\gamma$) and the like-sign top pair production at the LHC. We also pay special attention to the most recently measured $A^t_{FB}$ in the large top pair invariant mass region. We find that under the current experimental constraints both models can alleviate the deviation of $A^t_{FB}$ and, meanwhile, enhance the like-sign top pair production to the detectable level of the LHC. We also find that the two models give different predictions for the observables and their correlations, and thus they may even be distinguished by jointly studying these top quark observables.