Contributions of Vector-Like Quarks to $B \to X_s \gamma$ and $B_s^0 \bar B_s^0$ Mixing

Abstract

The radiative decay $\BSgamma$ and the mixing $\BsBs$ are discussed in the vector-like quark model which contains extra SU(2)-singlet quarks with the same electric charges as the up-type and down-type quarks. Constraints on the extended Cabibbo-Kobayashi-Maskawa matrix are obtained from the experimental results for the branching ratio of $\BSgamma$ . Within these experimental bounds, any value of the branching ratio can be accounted for by the contributions from the vector-like quarks. In sizable ranges of the model parameters, the mixing parameter for $\BsBs$ is much different from the prediction of the standard model.