Universalτ1/2(y)Isgur-Wise function at the next-to-leading order in QCD sum rules

We use QCD sum rules, in the framework of the heavy quark effective theory, to calculate the universal form factor ${\tau }_{1/2}\mathrm{}\left(y\right)\mathrm{}$ parametrizing the semileptonic transitions $\overrightarrow{B}{D}_{0}l\overline{\nu },$ $\overrightarrow{B}{D}_1^{*}l\overline{\nu },$ where $D_0$ and $D_1^{*}$ are the members of the excited charmed doublet with $J^P{=(0\mathrm{}}_{1/2}^{+}{,1\mathrm{}}_{1/2}^{+}).\mathrm{}$ We include two-loop corrections in the perturbative contribution to the sum rule, and present a complete next-to-leading order result. As a preliminary part of our analysis we also compute, up to order ${\alpha }_s,$ the leptonic constant $F^{+}$ of the doublet $D_0,$ $D_1^{*}.$ Finally, we discuss the phenomenological implications of this calculation.