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 jp and for the universal Isgur-Wise form factor. It is shown that renormalization group effects considerably enhance the prediction for jp and bring its asymptotic value in accordance with recent lattice results. Including finite mass corrections, the dependence of the physical decay constants on the meson mass is investigated. We obtain fD N 170 f 30 MeV and Jo 21 190 f 50 MeV. The origin of the break-down of the heavy quark expansion for fD is analyzed. In the case of heavy meson transition form factors, both the QCD and l/m~ 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. Submitted to Physical Review D ‘‘T Work supported by the Department of Energy, contract DE-AC03-76SF00515. t Research fellow of the BASF Aktiengesellschaft and the German National Scholarship Foundation