Predictions forB→D1(2420)ℓν¯andB→D2*(2460)ℓν¯at OrderΛQCD/mc,b

Exclusive semileptonic $B$ decays into $D_1$ and $D_2^{*}$ mesons are investigated including order ${\Lambda }_{\mathrm{QCD}}{/m}_{c,b}$ corrections using the heavy quark effective theory. At zero recoil, the ${\Lambda }_{\mathrm{QCD}}{/m}_{c,b}$ corrections can be written in terms of the leading Isgur-Wise function for these transitions, τ, and known meson mass splittings. We obtain an almost model independent prediction for the shape of the spectrum near zero recoil, including order ${\Lambda }_{\mathrm{QCD}}{/m}_{c,b}$ corrections. We determine $\tau \left(1\right)$ from the measured $B\to D_1\ell \overline{\nu }$ branching ratio. Implications for $B$ decay sum rules are discussed.