Exclusive $c\to s,d$ semileptonic decays of ground-state spin-1/2 and   spin-3/2 doubly heavy $cb$ baryons
  We evaluate exclusive semileptonic decays of ground-state spin-1/2 and spin-3/2 doubly heavy $cb$ baryons driven by a $c\to s,d$ transition at the quark level. We check our results for the form factors against heavy quark spin symmetry constraints obtained in the limit of very large heavy quark masses and near zero recoil. Based on those constraints we make model independent, though approximate, predictions for ratios of decay widths. 
C. Albertus, E. Hern\'andez, J. Nieves
hep-ph