B-\bar{B} Mixings and Rare B Decays in the Topflavour Model

We explore the impact of topflavour model to $B-\bar{B}$ mixings and rare decays of $B$ mesons. By the flavour-changing neutral current interactions of this model, the $B-\bar{B}$ mixing amplitudes are substantially affected while it is hard to investigate the effects on rare decays. Violation of the unitarity of the CKM matrix is also discussed. We find that the bound on $|V_{td}|$ can be stronger in this model by combining the experimental bound of the $B-\bar{B}$ mixing and the bound from violated unitarity.