B Meson Light-cone Distribution Amplitudes and Heavy-quark Symmetry∗

Recently systematic methods based on the QCD factorization have been developed for the exclusive B meson decays into light mesons (for other approaches see). Essential ingredients in this approach are the light-cone distribution amplitudes for the participating mesons, which constitute nonperturbative long-distance contribution to the factorized amplitudes. For the light mesons (π, K, ρ, K, etc.) appearing in the final state, systematic model-independent study of the light-cone distributions exists for both leading and higher twists. On the other hand, the light-cone distribution amplitudes for the B meson are not well-known at present and provide a major source of uncertainty in the calculations of the decay rates. In this work, we demonstrate that heavy-quark symmetry and constraints from the equations of motion determine a unique analytic solution for the B meson light-cone distribution amplitudes within the two-particle Fock states. We also derive the exact integral representations for the effects of higher Fock states with additional gluons. In the heavy-quark limit, the B meson matrix elements obey the heavy-quark symmetry, and is described by the heavy-quark effective theory (HQET). Following