Isospin symmetry breaking in B → K*γ decay due to an extra generation of vector quarks

The extra contributions due to an extra generation of vector-like quarks to the isospin symmetry breaking observable associated with the radiative B -> K*gamma decay is obtained. It is shown that this additional contribution is sensitive to the nonunitarity parameter U-sb, which is a measure of the the strength of the non-zero tree-level flavor changing neutral current in this model. The significance of this result is that, once accurate experimental results on the isospin asymmetry becomes available, one can constrain the U-sb independent of the mass of the extra quarks and so a much more stringent acceptable model parameter space could be obtained.