$B_d-\bar{B}_d$ mixing vs. $B_s-\bar{B}_s$ mixing with the anomalous $Wtb$ couplings

We explore the effects of the anomalous $tbW$ couplings on the $\bd$ mixing and recently measured $\bs$ mixing. The combined analysis of mixings via box diagrams with penguin decays provides strong constraints on the anomalous top quark couplings. We find the bound from the $\bd$ mixing data is stronger than that from the $\bs$ mixing.