Semileptonic $B \rightarrow \bar{D} $ transition in nuclear medium
  We study the semileptonic tree-level $B \rightarrow \bar{D}$ transition in the framework of QCD sum rules in nuclear medium. In particular, we calculate the in-medium form factors entering the transition matrix elements defining this decay channel. It is found that the interactions of the participating particles with the medium lead to a considerable suppression in the branching ratio compared to the vacuum. 
K. Azizi, N. Er, H. Sundu
hep-ph nucl-th