B -> X_s l+ l- in the vectorlike quark model

Abstract

We extend the standard model by adding an extra generation of isosinglet up- and down-type quark pair which engage in weak interactions only via mixing with the three ordinary quark families. It is shown that the generalized $4\times 4$ quark mixing matrix, which is necessarily nonunitary, leads to nonvanishing flavor changing neutral currents. We then proceed to investigate various distributions and total branching ratio of the inclusive B -> X_s l+ l- (l =e,\mu) rare B decays in the context of this model. It is shown that the shapes of the differential branching ratio and forward-backward asymmetry distribution are very sensitive to the value of the model parameters which are constrained by the experimental upper bound on BR(B -> X_s \mu^+ \mu^-). We also indicate that, for certain values of the dileptonic invariant mass, CP asymmetries up to 10% can be obtained.