CP Violation in Top Quark Pair Production at Hadron Colliders

Abstract

CP violating effects in top quark pair production at the future 2 TeV $p\bar p$ Tevatron and 14 TeV $pp$ LHC colliders are investigated. We study three kinds of CP violating sources:the supersymmetric CP-odd phase of the stop trilinear soft breaking term: $arg(A_t)$, the CP-odd parameter in two-Higgs doublet extensions of the standard model(2HDM), and the model-independent top quark chromoelectric dipole moment(CEDM), respectively. Optimal observables as well as simple observables are used. We find that it is possible to observe CP violating effects from $arg(A_t)$ in top quark pair production at the 2 TeV Tevatron with $\sim 30fb^{-1}$ integrated luminosity when $m_{\tilde{g}}\sim 200$ GeV. If the experimental systematic errors are sufficient small, the LHC with $\sim 150fb^{-1}$ can put a limit of order $10^{-1}$ on the phase $arg(A_t)$ and the CP-odd parameter in 2HDM by using optimal observables. The CEDM of the top quark can be measured to an accuracy of $10^{-18} cm g_s$ at the Tevatron and few $\times 10^{-20} cm g_s$ at the LHC.