Asymptotics of heavy-meson form factors

Using methods developed for hard exclusive QCD processes, we calculate the asymptotic behavior of heavy-meson form factors at large recoil. It is determined by the leading- and subleading-twist meson wave functions. For 1<|v·v'|mQ/Λ, they are dominated by two functions arising at order 1/mQ in the heavy-quark expansion, which are determined by the leading-twist wave function alone. The sum of these contributions describes the form factors in the whole region |v·v'|>1. As a consequence, there is an exact zero in the form factor for the scattering of longitudinally polarized B* mesons at some value v·v'∼mb/Λ, and an approximate zero in the form factor of B mesons in the timelike region (v·v'∼-mb/Λ). We obtain the evolution equations and sum rules for the wave functions of leading and subleading twist as well as for their moments. We briefly discuss applications to heavy-meson pair production in e+e- collisions. copyright 1997 The American Physical Society