The top quark charge asymmetry in tt̅γ production at the LHC

We consider the top quark charge asymmetry in the process pp → tt̅+γ at the 13 TeV LHC. The genuine tree level asymmetry in the qq̅ channel is large with about -12% . However, the symmetric gg channel, photon radiation off top quark decay products, and higher order corrections wash out the asymmetry and obscure its observability. In this work, we investigate these effects at next-to-leading order QCD and check the robustness of theoretical predictions. We find a sizable perturbative correction and discuss its origins and implications. We also study dedicated cuts for enhancing the asymmetry and show that a measurement is possible with an integrated luminosity of 150 fb^-1 .