Edge Charge Asymmetry in Top Pair Production at the LHC

In this brief report, we propose a new definition of charge asymmetry in top pair production at the LHC, namely the edge charge asymmetry (ECA). ECA utilizes the information of drifting direction only for single top (or anti-top) with hadronically decay. Therefore ECA can be free from the uncertainty arising from the missing neutrino in the $t\bar{t}$ event reconstruction. Moreover rapidity $Y$ of top (or anti-top) is required to be greater than a critical value $Y_{\rm C}$ in order to suppress the symmetric $t\bar{t}$ events mainly due to the gluon-gluon fusion process. In this paper ECA is calculated up to next-to-leading order QCD in the standard model and the choice of the optimal $Y_{\rm C}$ is investigated.