Nonspectator effects in B-> K^*+photon within the vector quark model

Abstract

The tree level FCNC due to the presence of an additional generation of vector quarks result in the leading order nonspectator contributions to rare B-> K^*+photon decay mode. These tree level contributions are sensitive only to b-> s nonunitary parameter U^{sb} and therefore, provide a direct constraint on this model parameter. We obtain the isospin asymmetry between \bar B^0->\bar K^{*0}+photon and B^--> K^{*-}+photon to be Δ_{0-}=-0.03*Re (U^{sb}/(a^c_7V_{tb}V^*_{ts})) and the direct CP asymmetry between B^+->K^{*+}+photon and B^--> K^{*-}+photon to be A_{CP}^{VQM}=0.27|U^{sb}/(V_{tb}V_{ts}^*)|*sinθ*sin{ϕ_s}, where θis the weak phase of U^{sb} and ϕ_s is the strong phase of decay amplitude. We predict a direct CP asymmetry of around a few percent if the current experimental difference between Δ_{0-} and Δ_{0+} is to be explained by the presence of the additional vector quarks.