Flavor signatures of complex anomalous tcZ couplings

In this work, we study the effects of anomalous tcZ couplings. Such couplings would potentially affect several neutral current decays of K and B mesons via Z-penguin diagrams. Using constraints from relevant observables in K and B sectors, we find that the 2σ upper bound on the branching ratio of B(t→ cZ) is 1.47 × 10 - 5 for real coupling and 1.91 × 10 - 4 for complex coupling. The current experimental upper bound from ATLAS and CMS collaborations on the branching ratio of t→ cZ is 2.4 × 10 - 4 and 4.9 × 10 - 4 at 95 % C.L., respectively. Hence the possibility of observation of t→ cZ decay at the level of 10 - 4 would imply the anomalous couplings to be complex. Such complex couplings should also show up its presence in other related decays. We find that an order of magnitude enhancement is possible in the branching ratio of KL→ πνν¯. Further, the complex tcZ coupling can also provide large enhancements in many CP violating angular observables in B→ K∗μ+μ- decay.