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 ${\ensuremath{\tau}}_{1/2}(y)$ parametrizing the semileptonic transitions $\stackrel{\ensuremath{\rightarrow}}{B}{D}_{0}l\overline{\ensuremath{\nu}},$ $\stackrel{\ensuremath{\rightarrow}}{B}{D}_{1}^{*}l\overline{\ensuremath{\nu}},$ where ${D}_{0}$ and ${D}_{1}^{*}$ are the members of the excited charmed doublet with ${J}^{P}{=(0}_{1/2}^{+}{,1}_{1/2}^{+}).$ 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 ${\ensuremath{\alpha}}_{s},$ the leptonic constant ${F}^{+}$ of the doublet ${D}_{0},$ ${D}_{1}^{*}.$ Finally, we discuss the phenomenological implications of this calculation.