Exclusive rare B-decays in the heavy quark limit

We calculate the rare B-decays B→K*γ and B→(K, K*)lanti l (l=e, μ, ν) in the limit when the qaurk masses mb, mc and ms are considered heavy. In this limit, the semileptonic decays B→Dlνl, B→D*lνl, D→Klνl, D→K*lνl and the mentioned rare B-decays are related. Experimental data on the semileptonic decays then provide both input information for the rare B-decays as well as an estimate of the error of our approximation. (orig.)