Determination of |V(ts)| from D ---> K* lepton neutrino and B ---> K+ gamma data via heavy quark symmetry and perturbative QCD

We use heavy quark effective theory (HQET) and perturbative QCD to study the heavy-meson--light-vector-meson transitions involved in D and B decays. HQET is used to relate the measured D\ensuremath{\rightarrow}${\mathit{K}}^{\mathrm{*}}$l\ensuremath{\nu} vector and axial-vector form factors at four-momentum transfer ${\mathit{q}}^{2}$=0 to the B\ensuremath{\rightarrow}${\mathit{K}}^{\mathrm{*}}$\ensuremath{\gamma} tensor and axial-tensor form factors at ${\mathit{q}}^{2}$=16.5 ${\mathrm{GeV}}^{2}$. Perturbative QCD is then used to find matching conditions for the B-meson form factors at ${\mathit{q}}^{2}$=0. A five parameter ``vector-dominance''-type fit of the two HQET form factors, consisting of single pole, double pole, and subtraction terms, is used to match the data at ${\mathit{q}}^{2}$=16.5 ${\mathrm{GeV}}^{2}$ to QCD at ${\mathit{q}}^{2}$=0. The values at ${\mathit{q}}^{2}$=0 are compared with recent data on the exclusive rate for B\ensuremath{\rightarrow}${\mathit{K}}^{\mathrm{*}}$\ensuremath{\gamma} decay to extract a value for the Cabibbo-Kobayashi-Maskawa matrix element \ensuremath{\Vert}${\mathit{V}}_{\mathit{t}\mathit{s}}$\ensuremath{\Vert}=0.026, with 23% experimental uncertainty, and 29% theoretical uncertainty from higher order QCD effects and violations of heavy quark symmetry.