Searching for $G^3$ in $t \tbar$ Production
  The triple gluon field strength operator $G^3$ represents the only genuinely gluonic CP conserving term which can appear at dimension-6 within an effective strong interaction Lagrangian. Previous studies of this operator have revealed that its effect on gluon scattering is surprisingly difficult to detect. In this article, we analyze the impact of $G^3$ upon top quark pair production. We find that it will generate observable cross section deviations from QCD at the LHC for even relatively small values of its coefficient. Furthermore, $G^3$ affects the transverse momentum distribution of the produced top quarks more strongly at high energies than dimension-6 four-quark and chromomagnetic moment terms in the effective Lagrangian. Top-antitop production at the LHC will therefore provide a sensitive and clean probe for the elusive triple gluon field strength operator. 
Peter Cho and Elizabeth Simmons