HEAVY-MESON FORM-FACTORS FROM QCD SUM-RULES

A consistent framework is developed for studying hadronic form factors of heavy mesons using QCD sum rules in the heavy-quark effective theory, including the next-to-leading-order renormalization-group improvement. Sum rules are derived for the asymptotic value of the meson decay constant f(P) and for the universal Isgur-Wise form factor. It is shown that renormalization-group effects considerably enhance the prediction for f(P) and bring its asymptotic value in accordance with recent lattice results. Including finite-mass corrections, the dependence of the physical decay constant on the meson mass is investigated. We obtain f(D) congruent-to 170 +/- 30 MeV and f(B) congruent-to 190 +/- 50 MeV. The origin of the breakdown of the heavy-quark expansion for f(D) is analyzed. In the case of heavy-meson transition form factors, both the QCD and 1/m(Q) corrections are moderate and under control. A sum rule for the renormalized Isgur-Wise function is derived and evaluated. The theoretical result is compared to experimental data.