Large effects on $\text{BsBs}$ mixing by vector-like quarks

Abstract

We calculate the contributions of the vector-like quark model to $\text{BsBs}$ mixing, taking into account the constraints from the decay $B\to X_s\gamma$. In this model the neutral bosons mediate flavor-changing interactions at the tree level. However, $\text{BsBs}$ mixing is dominated by contributions from the box diagrams with the top quark and the extra up-type quark. In sizable ranges of the model parameters, the mixing parameter $x_s$ is much different from the standard model prediction.

Comments: 11 pages, 4 figures, To be published in Phys. Rev. D