Regular Article – Theoretical Physics
Contributions to () couplings from CP violating flavor changing couplings
Facultad de Ciencias Físico-Matemáticas, Benemérita Universidad Autónoma de Puebla, C.P. 72570, Puebla, Pue, Mexico
2 Ingeniería en Mecatrónica, Universidad Politécnica de Puebla, Tercer Carril del Ejido Serrano s/n, San Mateo Cuanalá, Juan C. Bonilla, Puebla, Puebla, Mexico
Accepted: 30 March 2021
Published online: 10 April 2021
The one-loop contributions to the trilinear neutral gauge boson couplings (), parametrized in terms of one CP-conserving and one CP-violating form factors, are calculated in models with CP-violating flavor changing neutral current couplings mediated by the Z gauge boson and an extra neutral gauge boson . Analytical results are presented in terms of Passarino-Veltman scalar functions. Constraints on the vector and axial couplings of the Z gauge boson and are obtained from the current experimental data on the decays. It is found that in the case of the vertex the only non-vanishing form factor is , which can be of the order of , whereas for the vertex both form factors and are non-vanishing and can be of the order of and , respectively. Our estimates for and are smaller than those predicted by the standard model, where is absent up to the one loop level. We also estimate the form factors arising from both diagonal and non-diagonal couplings within a few extension models. It is found that in the diagonal case is the only non-vanishing form factor and its real and imaginary parts can be of the order of – and –, respectively, with the dominant contributions arising from the light quarks and leptons. In the non-diagonal case can be of the order of , whereas can reach values as large as –, with the largest contributions arising from the couplings.
© The Author(s) 2021
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