Signature of same-sign top pair production mediated by a nonuniversal   $Z^\prime$ with QCD next-to-leading accuracy at the LHC
  We present a detailed study of the same-sign top pair production mediated by a non-universal $Z^\prime$ including production and decay at the Large Hadron Collider (LHC) at the QCD next-to-leading order (NLO) level, using the narrow width approximation and helicity amplitudes method. We find that the QCD NLO corrections can loose the constraint on the model parameters and reduce the dependence of the total cross sections on the factorization scale significantly. We also study the signature and backgrounds of the process at the NLO level. In order to suppress the backgrounds, we further investigate the difference between the production rates of the positively and negatively charged dilepton at the LHC, and find that the same-sign dilepton signal of the new physics could be discovered more easily. 
Bo Hua Li, Chong Sheng Li, Hai Tao Li, Yong Chuan Zhan, Yue Zhang and   Jian Wang
hep-ph hep-ex