Investigation of the rare exculsive B_c^ast rightarrow D_(s)~ν bar{ν} decays in the faramework of the QCD sum rules

Exclusive $B_c^\ast \rightarrow D_{s}~\nu \bar{\nu}$ decay is studied in the framework of the three--point QCD sum rules approach. The two gluon condensate contributions to the correlation function are calculated and the form factors of this transition are found. The decay width and total branching ratio for this decay is also calculated.