Revisiting the top quark chromomagnetic dipole moment in the SM

We revisit the anomalous chromomagnetic dipole moment in the Standard Model and show that its triple gluon vertex contribution, with the on-shell gluon ( q 2 = 0 ), generates an infrared divergent pole. Consequently, the chromomagnetic dipole should not be perturbatively evaluated at q 2 = 0 . Focusing on this top quark anomaly, denoted as μ ^ t ( q 2 ) , we compute it with the off-shell gluon with a large momentum transfer, just as the α s ( m Z 2 ) convention scale, for both spacelike q 2 = - m Z 2 and timelike q 2 = m Z 2 cases. We found that μ ^ t ( - m Z 2 ) = - 0.0224 - 0.000925 i and μ ^ t ( m Z 2 ) = - 0.0133 - 0.0267 i . Our Re μ ^ t ( - m Z 2 ) matches well with the current experimental value μ ^ t Exp = - 0 . 024 - 0.009 + 0.013 ( stat ) - 0.011 + 0.016 ( syst ) , and the Im μ ^ t ( - m Z 2 ) part is induced by flavour changing charged currents.