$b\to s(d)\gamma$ with a Vector-like Quark as Fourth-generation

Abstract

We study the implications of a vector-like quark, especially a down-type vector-like quark in $b\to s(d)\gamma$ including the neutral Higgs in the calculation. After analyzing some possible constraints for the mixing, the contribution may be significant for the $b\to d\gamma$, but not for the $b\to s\gamma$. We also find that the FCNC among ordinary quarks vanishes for a special form of down-type quark mass matrix.

Comments: 4 figures are included and 1 figure is excluded