Z mediated flavor changing neutral currents with a fourth vectorlike family

We discuss Z mediated flavor changing neutral currents within a model where the hierarchical quark and
lepton masses are explained via a fourth vectorlike family, together with a scalar sector consisting of two
Higgs doublets augmented by a gauge singlet scalar field that spontaneously breaks an extra global Uð1Þ0
symmetry. The Z mediated flavor violating interactions arise from the mixings between the SM fermions
and the vectorlike fermions, where the mixing is discussed in an analytic approximation and also exactly
numerically. We first discuss charged lepton flavor violating (CLFV) τ → μγ, τ → 3μ and Z → μτ decays
and find that they cannot significantly constrain the masses of charged vectorlike leptons. However, the
790 GeV mass bound arising from collider searches on vectorlike lepton doublets can set further constraints
on the model parameter space. We also consider rare t → cZ decays as well as unitarity violation in the
CKM mixing in order to constrain the quark sector of the model under consideration.