ar X iv : h ep - p h / 97 12 35 6 v 1 1 2 D ec 1 99 7 Determination of the CKM matrix by semileptonic rare B - decays ∗

The possibility to test the unitarity triangle of CKM matrix is examined by using the semileptonic rare B decays, B → Xq l l− with q = d, s and l’s are leptons. The discussion is emphasized on the CP asymmetry in the framework of standard and beyond the standard models. For the beyond standard model, a minimal extension of the standard model containing an additional isosinglet charge (-1/3) charge quark, which leads to a deviation from CKM unitarity, is considered. As the results, in the standard model the CP asymmetry is visible only for B → Xd l l−, while in the latter model it is sizeable even for B → Xs l l−.