Revisiting the top quark chromomagnetic dipole moment in the SM

Abstract

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 ${\hat{\mu }}_t(q^2)$, we compute it with the off-shell gluon with a large momentum transfer, just as the ${\alpha }_s(m_Z^2)$ convention scale, for both spacelike $q^2=-m_Z^2$ and timelike $q^2=m_Z^2$ cases. We found that ${\hat{\mu }}_t(-m_Z^2)$ $=$ $-0.0224$ $-0.000925i$ and ${\hat{\mu }}_t(m_Z^2)$ $=$ $-0.0133$ $-0.0267i$. Our $\mathrm{Re}{\hat{\mu }}_t(-m_Z^2)$ matches well with the current experimental value ${\hat{\mu }}_t^{\mathrm{Exp}}=-0.024_{-0.009}^{+0.013}(\mathrm{stat}{)}_{-0.011}^{+0.016}(\mathrm{syst})$, and the $\mathrm{Im}{\hat{\mu }}_t(-m_Z^2)$ part is induced by flavour changing charged currents.

arXiv comment20 pages, 4 figures, this version matches with the published one

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Cited by in corpus (5)

• Chromomagnetic and chromoelectric dipole moments of quarks in the reduced 331 model
• Bounds on the absorptive parts of the chromomagnetic and chromoelectric dipole moments of the top quark from LHC data
• The top quark chromomagnetic dipole moment in the SM from the 4-body vertex function
• Off-shell chromomagnetic dipole moments in the SM at and beyond the $Z$ gauge boson mass scale
• Probing top quark anomalous moments in $W$ boson associated single top quark production at the LHC using polarization and spin correlation