Form factors and decay rate of $B_c^\ast \rightarrow D_{s}~l^+ l^-$   decays in the QCD sum rules
  Rare exclusive $B_c^\ast \rightarrow D_{s}~l^+ l^-$ decays are analyzed in the framework of the three--point QCD sum rules approach. The two gluon condensate corrections to the correlation function are included and the form factors of this transition are evaluated. Using the form factors, the decay width and integrated decay rate for these decays are also calculated. 
K. Zeynali, V. Bashiry, F. Zolfagharpour
hep-ph