Semileptonic decays in the limit of a heavy daughter quark
  The rate of the semileptonic decay b to c l v is calculated with order alphas^2 accuracy, as an expansion around the limit of equal masses of the b and c quarks. Recent results obtained around the limit of the c-quark much lighter than b are confirmed. Details of the new expansion method are described. 
Matthew Dowling, Jan H. Piclum, and Andrzej Czarnecki