Lattice-constrained parametrizations of form factors for semileptonic and rare radiative B decays

We describe all the form factors for semileptonic and radiative B decays to the same light vector meson with just two parameters and the two form factors for semileptonic B decays to a light pseudoscalar meson with a further two or three parameters. This provides simple parametrizations of the form factors for the physical <(B)over bar (0)> --> <rho(+)l(-)(v)over bar (l)>, <(B)over bar (0)> --> <pi(+)l(-)(v)over bar (l)> and (B) over bar --> K*gamma decays. The parametrizations are consistent with heavy quark symmetry, kinematic constraints and lattice results, which we use to determine the parameters. In addition, we test versions of the parametrizations consistent (or not) with light-cone sum rule scaling relations at q(2) = 0. (C) 1998 Elsevier Science B.V.