Model independent results for $B\to D_1(2420)\ell \bar{\nu }$ and $B\to D_2^{\ast }(2460)\ell \bar{\nu }$ at order ${\Lambda }_{QCD}/m_{c,b}$

Abstract

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

Comments: 11 pages, revtex