Test of the chiral structure and FCNC in the quark sector by radiative B meson decays

Abstract

We study the effects of a vector-like SU(2) quark doublet as a fourth generation. In this model we examine the chiral structure and the FCNC in the quark sector by using radiative B meson decays in the allowed region for parameters from $R_b={\Gamma }_{qq}/{\Gamma }_{had.}$. We compute the ratio $R=Br(b\to d\gamma )/Br(b\to s\gamma )$ in the model which realizes a different chiral structure as well as FCNC. The constraints has been extracted from the experimental results of B meson decays, the $T_{new}$ parameter of oblique corrections and $R_b$. Under the natural assumption that the violation of the $V-A$ structure in the light-quark sector is small, we can determine the allowed region for most of the mixings parameters and the vector-like quark masses. We show that there will be significant deviations in $R$ from the SM prediction due to the FCNC's and the violation of the $V-A$ structure.

Comments: 19 pages, figures included, revised version for publication (accepted in Int. Jour. Mod. Phys. A)