Z-Z' Mixing and Z-Mediated FCNCs in SU(3)_C x SU(3)_L x U(1)_X Models

Understand

Most of the existing analyses of FCNC processes in the 331 models, based on the gauge group SU(3)_C x SU(3)_L x U(1)_X, take only into account tree-level exchanges of a new heavy neutral gauge boson Z'.

• However due to the Z-Z' mixing also corresponding contributions from Z boson are present that are usually neglected.
• We calculate the impact of these contributions on Delta F=2 processes and rare K, B_s and B_d decays for different values of a parameter beta, which distinguishes between various 331 models and for different fermion representations under the SU(3)_L group.
• We find a general expression for the Z-Z' mixing in terms beta, M_Z, M_Z' and tan(bar{beta}), familiar from 2 Higgs Doublet models, that differs from the one quoted in the literature.