Flavor changing neutral current in rare top quark decay t → cl in generic Z' and left-right symmetric models

We study the rare top decay t → cl, which involves flavor violation, as a possible probe of new physics. This decay is analyzed with the simplest Standard Model (SM) extensions with additional gauge symmetry U(l) or SU(2), known as generic Z' model or left-right symmetric model, respectively. The considered models allow to obtain this decay at tree level through Flavor Changing Neutral Currents (FCNC). We have considered diagonal non-universal couplings for up-type quark sector and found that BR(t → cl) for 1 TeV < M_z' < 3 TeV can be of order ∼ 10⁻¹¹ in generic Z' model or ∼ 10⁻¹² in left-right symmetric model.