Top Quark Forward-Backward Asymmetry and Same-Sign Top Quark Pairs

The top quark forward-backward asymmetry measured at the Tevatron collider shows a large deviation from standard model expectations. Among possible interpretations, a nonuniversal $Z^{\prime }$ model is of particular interest as it naturally predicts a top quark in the forward region of large rapidity. To reproduce the size of the asymmetry, the couplings of the $Z^{\prime }$ to standard model quarks must be large, inevitably leading to copious production of same-sign top quark pairs at the energies of the Large Hadron Collider (LHC). We explore the discovery potential for $tt$ and $ttj$ production in early LHC experiments at 7–8 TeV and conclude that if no $tt$ signal is observed with $1{\mathrm{fb}}^{-1}$ of integrated luminosity, then a nonuniversal $Z^{\prime }$ alone cannot explain the Tevatron forward-backward asymmetry.