Semileptonic Decay of $B$-Meson into $D^{**}$ and the Bjorken Sum Rule
  We study the semileptonic branching fraction of $B$-meson into higher resonance of charmed meson $D^{**}$ by using the Bjorken sum rule and the heavy quark effective theory(HQET). This sum rule and the current experiment of $B$-meson semileptonic decay into $D$ and $D^*$ predict that the branching ratio into $D^{**}l\nu_l$ is about 1.7\%. This predicted value is larger than the value obtained by the various theoretical hadron models based on the HQET. 
Masahisa Matsuda(1), Tsuyoshi B. Suzuki(2) ((1) Department of Physics   and Astronomy, Aichi University of Education, Kariya...