Semileptonic decay of B-meson into D∗∗ and the Bjorken sum rule

We study the semileptonic branching fraction of the B-meson into the higher resonance of the charmed meson D∗∗ by using the Bjorken sum rule and the heavy quark effective theory (HQET). This sum rule and the current experiment of the B-meson semileptonic decay into D and D∗ predict that the branching ratio D∗∗lνl is about 1.7%. This predicted value is larger than the value obtained by various models.