Corrections to the Bjorken and Voloshin sum rules

We calculate near zero recoil the order αs corrections to the Bjorken and Voloshin sum rules that bound the B→D(*)scr(l)bar ν form factors. These bounds are derived by relating the result of inserting a complete set of physical states in a time-ordered product of weak currents to the operator product expansion. The sum rules sum over physical states with excitation energies less than a scale Δ. We find that the corrections to the Bjorken bound are moderate, while the Voloshin bound receives sizable corrections enhanced by Δ/ΛQCD. With some assumptions, we find that the slope parameter for the form factor hA1 in B→D*scr(l)bar ν decay satisfies 0.4 approx-lt ρA12 approx-lt 1.3. copyright 1997 The American Physical Society