Vector quark model and B→X_sγ decay

We study the B meson radiative decay B→X_sγ in the vector quark model. Deviation from the standard model arises from the nonunitarity of the charged current Kobayashi-Maskawa matrix and related new flavor changing neutral current interactions. We establish the relation between the nonunitarity of the charged current mixing matrix and the mixing among the vector quark and ordinary quarks. We also explicitly make the close connection between this nonunitarity and the flavor changing neutral currents. The complete calculation including the leading logarithmic QCD correction is carefully carried out. Using the most updated data and the next to leading order theoretical calculation, the branching fraction of the observed B meson radiative decay places a limit on the mixing angles as stringent as that from the process B→Xμμ̄.