LATTICE-CONSTRAINED PARAMETRIZATIONS OF FORM-FACTORS FOR SEMILEPTONICAND RARE RADIATIVE B-DECAYS

We describe all the form factors for semileptonic and radiative B deca ys 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 parametri zations of the form factors for the physical <(B)over bar (0)> --> <rh o(+)l(-)(v)over bar (l)>, <(B)over bar (0)> --> <pi(+)l(-)(v)over bar (l)> and (B) over bar --> Kgamma decays. The parametrizations are con sistent with heavy quark symmetry, kinematic constraints and lattice r esults, 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.