T-odd gluon-top-quark effective couplings at the CERN large hadron collider

Abstract

The T -odd top-quark chromoelectric dipole moment ( t CEDM) is probed through top-quark-pair production via gluon fusion at the CERN Large Hadron Collider (LHC) by considering the possibility of having polarized protons. The complete analytic expressions for the tree-level helicity amplitudes of gg → tt is also presented. For the derived analytic results we determine the 1-σ statistical sensitivities to the t CEDM form factor for (i) typical CP -odd observables composed of lepton and anti-lepton momenta from t and t semileptonic decays for unpolarized protons, and (ii) a CP -odd event asymmetry for polarized protons by using the so-called Berger-Qiu (BQ) parametrization of polarized gluon distribution functions. We find that at the CERN LHC, the CP -odd energy and angular correlations can put a limit of 10 −18 to 10 −17 g s cm on the real and imaginary parts of the t CEDM, while the simple CP -odd event asymmetry with polarized protons could put a very strong limit of 10 −20 g s cm on the imaginary part of the t CEDM.