I point out that B → Xq l+ l- decays (q = s, d) are sensitive probes of possible violation of CKM unitarity. I compute the decay rates and asymmetries in a minimal extension of the Standard Model containing an additional isosinglet charge (-1/3) quark, which leads to a deviation from CKM unitarity. It is shown that even for small mixing ratios |zqb/(Vtq*Vtb)|O(10-2), the contribution of the tree-levelZ-FCNC appearing in the model should change the rates and asymmetries significantly. Especially theCP asymmetry, ACP (B → Xs l+ l-), can be enhanced to be few percents, while in the standard model the size is less thanO(1023). On the other hand, ACP (B → Xs l+) is not altered so much. Constraints for the mixing ratios are extracted from the experiments of B→Xs ΰ for q = s and B0d-B0d mixing for q = d under the natural assumption that the couplings of the tree-level Zff are almost unity,i.e.zαα ∼ 1.
Determination of Kobayashi-Maskawa matrix elements
Extensions of electroweak gauge sector
Decays of bottom mesons
Leptonic and semileptonic decays
This is a preview of subscription content, log in to check access.
Branco G. C. andLavoura L.,Nucl. Phys. B,278 (1986) 738;Lavoura L. andSilva J. P.,Phys. Rev. D,47 (1993) 2046;Barger V.,Berger M. S. andPhilips R. J. N.,Phys. Rev. D,52 (1995) 1663.ADSCrossRefGoogle Scholar
Hewett J. L. andRizzo T. G.,Phys. Rep.,183 (1989) 193;Bento L.,Branco G. C. andParada P. A.,Phys. Lett.,267 (1991) 95.ADSCrossRefGoogle Scholar