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

We examine the chiral structure and the FCNC in the quark sector by using radiative $B$ meson decays. We compute the ratio $R = {Br (b \rightarrow d electroweak SM which realize different chiral structure as well as FCNC by adding one doublet vector-like quark as fourth generation. Any constraints has been extracted from the experiment results of $B$ meson decays, $T_{\rm new}$ parameter of oblique corrections and $R_q = {\Gamma_{qq}}/{\Gamma_{\rm had.}}$. Under a natural assumption that the violation of $V-A$ structure in the light-quarks sector is small, we can determine the allowed region of most of the mixings parameters and also the vector-like quark masses. We show that there will be significant deviations in $R$ from the SM's due to the FCNC's and the violation of $V-A$ structure