Sum rules for 1/m corrections to the form factors of semileptonic B decays

Semileptonic B decays are described by the Isgur-Wise form factor to the leading order in 1/m; four new functions appear in the first order [Luke]. Values of these functions are crucial for the applicability of the whole approach to processes involving c quark. We obtain the sum rules for three subleading form factors from the QCD sum rules with finite masses by expanding to the first order in 1/m. The results respect the pattern of the first 1/m corrections established in HQET, and obey the Luke's theorem. The numerical estimates show that 1/m_c corrections are sizable but not catastrophic.