QCD sum rules analysis of the rare $B_c \rar X\nu\bar{\nu}$ decays
  Taking into account the gluon correction contributions to the correlation function, the form factors relevant to the rare $B_c \rar X \nu\bar{\nu}$ decays are calculated in the framework of the three point QCD sum rules, where $X$ stands for axial vector particle, $AV(D_{s1})$, and vector particles, $V(D^*,D^*_s)$. The total decay width as well as the branching ratio of these decays are evaluated using the $q^2$ dependent expressions of the form factors. A comparison of our results with the predictions of the relativistic constituent quark model is presented. 
K. Azizi, R. Khosravi, V. Bashiry