  Understanding the composition of final states in $B \to X_c l \nu$ could help
to get a feedback on the persisting disagreement between exclusive and
inclusive determinations of $V_{cb}$. In particular the series of orbital
excitations $D^{**}$ and radial excitations ($D'$, $D^*\,'$) has received a lot
of attention; a misinterpretation as a scalar state of the ($D' \to D \pi$)
spectrum tail could have induced an experimental overestimate of the broad
states contribution to the total $B \to X_c l \nu$ width with respect to
theoretical expectations, all of them made however in the infinite mass limit:
it is the so-called 1/2 vs 3/2 puzzle. We describe first attempts to measure on
the lattice form factors of $B \to D^{**} l \nu$ at realistic quark masses.
Cleaner processes, like hadronic decays $B \to D^{**} \pi$ and semileptonic
decays $B_s \to D_s^{**} l \nu$ in the strange sector have recently been
examined by phenomenologists, putting new interesting ideas on those issues
with, again, the need of lattice inputs.
