QCD Sum Rules for Exclusive Decays of Heavy Mesons

Abstract

Applications of QCD sum rules to exclusive decays of heavy mesons are reviewed. In detail, we discuss the calculations of the B and $D$ decay constants, the heavy-to-light form factors $f^+(p^2)$ and $f^0(p^2)$, and the strong couplings $g_{B^*B\pi}$ and $g_{D^*D\pi}$. Predictions are presented for the semileptonic weak decays $B \to \pi \bar{l} \nu_l$ and $B \to \rho \bar{l} \nu_l$, and used to extract $V_{ub}$ from the measured decay widths. Results are also shown on $D \to \pi \bar{l} \nu_l$ and $D^* \to D \pi$. Furthermore, we reconsider the factorization hypothesis in nonleptonic two-body decays, and describe a sum rule estimate of the nonfactorizable contribution to the amplitude of $B \to J/\psi K$.