Revisiting the top quark chromomagnetic dipole moment in the SM

• Published in: European physical journal plus 2021-02, Vol.136 (2), p.164, Article 164
• Main Authors: Aranda, J. I., Cisneros-Pérez, T., Montaño, J., Quezadas-Vivian, B., Ramírez-Zavaleta, F., Tututi, E. S.
• Format: Article
• Language: English
• Subjects: Applied and Technical Physics; Atomic; Complex Systems; Condensed Matter Physics; Dipole moments; Flavor (particle physics); Gluons; Mathematical and Computational Physics; Molecular; Momentum transfer; Optical and Plasma Physics; Physics; Physics and Astronomy; Quarks; Regular Article; Standard model (particle physics); Theoretical
• ISSN: 2190-5444; 2190-5444
• DOI: 10.1140/epjp/s13360-021-01102-x

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.