HQET and Form Factor Effects in B rarrow K(*) ell+ell#minus#

We examine the rates for the exclusive decays B rarrow K* ell+ell-. We use the scaling predictions of the heavy quark effective theory to extract the necessary form factors from fits to various combinations of data. These data include the D rarrow K*ellν semileptonic decays, as well as the nonleptonic decays BrarrowK*ψprime and the rare decay B rarrow K*γ. We use different parametrizations of form factors, and find that integrated decay rates are not very sensitive to the forms chosen. However, the decay spectra and the forward-backward asymmetry in B rarrow K*ell+ell- are sensitive to the forms chosen for the form factors, while the lepton polarization asymmetry in bar B0 rarrow bar K0 μ+ μ- is largely independent of the choice of form factors. Contributions from charmonium resonances dominate the spectra and integrated rates. In our best scenario, we find Br(bar B0) rarrow bar K0 μ+μ- = 2.0 ± 0.3 times 10-6 and Br(bar B0 rarrow bar K*0 μ+ μ-) = 8.1 ± 2.0 x 10-6. We also make predictions for other polarization observables in these decays